Mandiant has observed a new ALPHV (aka BlackCat ransomware) ransomware affiliate, tracked as UNC4466, target publicly exposed Veritas Backup Exec installations, vulnerable to CVE-2021-27876, CVE-2021-27877 and CVE-2021-27878, for initial access to victim environments. A commercial Internet scanning service identified over 8,500 installations of Veritas Backup Exec instances that are currently exposed to the internet, some of which may still be unpatched and vulnerable. Previous ALPHV intrusions investigated by Mandiant primarily originated from stolen credentials suggesting a shift to opportunistic targeting of known vulnerabilities. This blog post covers the UNC4466 attack lifecycle, indicators, and detection opportunities.

ALPHV emerged in November 2021 as a ransomware-as-a-service that some researchers have claimed is the successor to BLACKMATTER and DARKSIDE ransomware. While some ransomware operators enacted rules to avoid impacting critical infrastructure and health entities, ALPHV has continued to target these sensitive industries.

Timeline

• In March 2021, Veritas published an advisory reporting three critical vulnerabilities in Veritas Backup Exec 16.x, 20.x and 21.x.
• On September 23, 2022, a METASPLOIT module was released which exploits these vulnerabilities and creates a session which the threat actor can use to interact with the victim system.
• On October 22, 2022, Mandiant first observed exploitation of the Veritas vulnerabilities in the wild.

Attack Phases

Initial Compromise and Establish Foothold

In late 2022, UNC4466 gained access to an internet-exposed Windows server, running Veritas Backup Exec version 21.0 using the Metasploit module `exploit/multi/veritas/beagent_sha_auth_rce`. Shortly after, the Metasploit persistence module was invoked to maintain persistent access to the system for the remainder of this intrusion.

Internal Reconnaissance

After gaining access to the Veritas Backup Exec server, UNC4466 used Internet Explorer, the browser installed by default on older Windows systems, to download Famatech’s Advanced IP Scanner from its website, hxxps://download.advanced-ip-scanner[.]com. This tool is capable of scanning individual IP addresses or IP address ranges for open ports, and returns hostnames, operating system and hardware manufacturer information.

UNC4466 also made use of ADRecon to gather network, account, and host information in the victim’s environment. When executed by a privileged domain account, ADRecon generates several reports about the Active Directory environment, including the Trusts, Sites, Subnets, password policies, user and computer account listings. These reports can be generated in a variety of formats, including CSV, XML, JSON, and HTML.

Ingress Tool Transfer

UNC4466 made heavy use of the Background Intelligent Transfer Service (BITS) to download additional tools such as LAZAGNE, LIGOLO, WINSW, RCLONE, and finally the ALPHV ransomware encryptor.

Command and Control

UNC4466 leveraged SOCKS5 tunneling to communicate with compromised systems in the victim network. This technique is typically used to evade network defenses or other preventative network controls. Two separate tools were deployed to execute this technique, LIGOLO and REVSOCKS.

Escalate Privileges

The threat actor utilized multiple credential access tools, including Mimikatz, LaZagne and Nanodump to gather clear-text credentials and credential material.

In November 2022, UNC4466 utilized the MIMIKATZ Security Support Provider injection module (`MISC::MemSSP`). This module collects credentials in clear text as they are used, by manipulating the Local Security Authority Server Service (LSASS) on victim systems. This module creates a file named `C:\Windows\System32\mimilsa.log`.

[Nanodump] was also used to dump LSASS memory. Like the examples shown on Helpsystems' GitHub page, the output file specified was a file in the `C:\Windows\Temp` directory.

Defense Evasion

During operations, UNC4466 takes steps to evade detection. Apart from clearing event logs, UNC4466 also used the built in Set-MpPrefernce cmdlet to disable Microsoft Defender’s real-time monitoring capability.

UNC4466 made use of BITS transfers (using the Start-BitsTransfer PowerShell cmdlet) to download various resources to the staging directory `c:\ProgramData`. Using this technique, SOCKS5 tunneling tools, REVSOCKS and LIGOLO were downloaded from their official GitHub repositories.

Complete Mission

UNC4466 deploys the Rust-based ALPHV ransomware. In Late 2022, UNC4466 added immediate tasks to the default domain policy. These tasks were configured to perform actions which disabled security software, downloaded the ALPHV encryptor, then execute it.

Exposure

As of this blog post's date, one commercial Internet scanning service reported over 8500 IP addresses which advertise the "Symantec/Veritas Backup Exec ndmp" service on the default port 10000, as well as port 9000 and port 10001. While this search result does not directly identify vulnerable systems, as the application versions were not identifiable, it demonstrates the prevalence of Internet exposed instances that could potentially be probed by attackers.

Detection Opportunities

Defenders should place priority on monitoring internet-exposed Veritas Backup Exec Windows installations, for versions before 21.2. Mandiant observed the exploitation of Veritas Backup Exec can leave a noticeable imprint on the Backup Exec log files. Where feasible, these log files should be forwarded to a SIEM or similar technology which enables detection and alerting when certain events are recorded.

In addition to any available network connection logging, Veritas Backup Exec logs will record evidence of connections to remote systems.

These connections should be triaged for any unknown IP addresses. Additionally, these logs can also record the execution of suspicious pre and post backup job commands.

UNC4466

• DS0015 - Application log
  • Backup Exec logs
    • Connections to unknown IP addresses
    • Suspicious pre or post job commands being set (SetPreCommandEnvironment/ SetPostCommandEnvironment). E.g: C:\Windows\System32\cmd.exe /c "C:\Windows\Temp\UNKNOWN_EXEC.exe”
  • Windows Event Logs
    • Suspicious BITS transfers with the source argument targeting unknown hosts and GitHub repositories.
    • Pre-ransomware activity: deletion of volume shadow copies
• DS0017 – Command
  • Disabling AMSI: use of Set-MpPreference PowerShell cmdlet
  • Ingress tool transfer: Use of Start-BitsTransfer PowerShell cmdlet
• DS0022 – File
  • New Executables created in staging directories: C:\ProgramData, C:\Windows\Temp, C:\Windows\Tasks
• DS0024 – Windows Registry
  • Modification of Registry run keys

Outlook

Mandiant recommends implementing secure access controls, segmenting networks, enabling multi-factor authentication, and regularly testing and evaluating backup strategies to limit the impact of a ransomware attack. Additionally, organizations should inventory externally facing services and reduce the attack surface available to attackers.

Acknowledgements

With special thanks to Nick Richard for technical review.

MITRE ATT&CK

Mandiant has observed UNC4466 use the following techniques:

Indicators of Compromise