Magic Hound Exploiting Old Microsoft Exchange ProxyShell Vulnerabilities

THREAT LEVEL: Red.

For a detailed advisory, download the pdf file here

APT35 aka Magic Hound, an Iranian-backed threat group, has begun using Microsoft Exchange ProxyShell vulnerabilities as an initial attack vector and to execute code through multiple web shells. The group has primarily targeted organizations in the energy, government, and technology sectors based in the United States, the United Kingdom, Saudi Arabia, and the United Arab Emirates, among other countries.

The threat actor exploits the Microsoft Exchange ProxyShell vulnerabilities (CVE-2021-34473, CVE-2021-34523, and CVE-2021-31207) to gain initial access to create web shells and disable antivirus services on the victim’s system.  To gain persistence in the environment, the threat actor employs both account creation and scheduled tasks. For future re-entry, the account is added to the “remote desktop users” and “local administrator’s users” groups. The threat actors use PowerShell to issue multiple commands to disable Windows Defender. Then they create a process memory dump from LSASS.exe that is zipped before exfiltration via web shell.  The threat actor uses native Windows programs like “net” and “ipconfig” to enumerate the compromised server. A file masquerading as dllhost.exe is used to access certain domains for command and control. Therefore, data can be exfiltrated by the threat actor which could potentially resulting in information theft and espionage.

The Microsoft Exchange ProxyShell vulnerabilities have been fixed in the latest updates from Microsoft. Organizations can patch these vulnerabilities using the patch links given below.

The MITRE TTPs commonly used by APT35 are:

TA0001: Initial AccessTA0002: ExecutionTA0003: PersistenceTA0004: Privilege EscalationTA0005: Defense EvasionTA0006: Credential AccessTA0007: DiscoveryTA0011: Command and ControlT1190: Exploit Public-Facing ApplicationT1003: OS Credential DumpingT1098: Account ManipulationT1078: Valid AccountsT1105: Ingress Tool TransferT1036: MasqueradingT1036.005: Masquerading: Match Legitimate Name or LocationT1543: Create or Modify System ProcessT1543.003: Create or Modify System Process: Windows ServiceT1505: Server Software ComponentT1505.003: Server Software Component: Web ShellT1082: System Information DiscoveryT1016: System Network Configuration DiscoveryT1033: System Owner/User DiscoveryT1059: Command and Scripting InterpreterT1059.003: Command and Scripting Interpreter: Windows Command Shell

Actor Details

Vulnerability Details

Indicators of Compromise (IoCs)

Patches

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-31207

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-34473

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-34523

References

https://thedfirreport.com/2022/03/21/apt35-automates-initial-access-using-proxyshell/