22 Minutes: Compromise to Containment

The incident occurred as a result of social engineering and where an employee unknowingly downloaded a malicious file which spread laterally across our environment. eSentire was able to quickly identify the threat through a combination of their machine learning platform and security analysts, who worked with us to quarantine and isolate. Given our business, the potential for financial and reputational impact was significant and this helps easily justify our investment in eSentire’s solution to our Board.

Head of IT Infrastructure,
UK-headquartered investment management company

Patient Zero

At the onset of the incident, the eSentire SOC received an alert from eSentire MDR for Endpoint that a JavaScript file was being downloaded to a computer on our financial client’s network. The SOC team began investigating and, with the help of machine learning and eSentire MDR for Network, they were able to follow the threat actor’s activity and quickly contain the threat.

Further investigation showed that, on the client side, Patient Zero had unknowingly downloaded and launched a malicious JavaScript file via Internet Explorer. Our SOC team observed that the network traffic captured at the time of compromise indicated that a potentially malicious web redirect via a website related to the SocGholish cybercrime campaign may have instigated the infection.

Once the malicious JavaScript file executed, it downloaded two other tools, one of which took two screenshots of the infected machine’s desktop. The SOC team saw in the network traffic that the screen shots were sent back to the attacker. This is a common “staging” tactic used by attackers to see if their payload is being opened in a sandbox. First the malicious script is executed, followed by the staging tactic test to see whether the environment is a sandbox so they do not expose their malware. Then, if safe, the attacker’s next step is to execute the malware.

The second tool downloaded by the initial JavaScript script was a remote control launcher. It was saved to the disk, renamed and then executed. This process triggered a malware alert from the SOC to the client. Once executed, it launched the built-in Windows Remote Access Tool which was recorded establishing a connection to an external channel, which is the likely command-and-control channel that was used for the malicious activity that immediately followed.

Just a few seconds after the remote control session was created via the Remote Assistance tool, some persistent malware was installed on the victim host. From there, lateral movement began.

Lateral movement

The lateral movement phase began approximately 10 minutes after persistence was established on Patient Zero. An encoded PowerShell command was executed that downloaded an RC4-encrypted second-stage PowerShell script and launched it. As soon as the attacker used a PowerShell command, eSentire’s proprietary BlueSteel machine learning tool picked up on the suspicious activity and another alert was generated.

The command was executed under Patient Zero’s normal user account, without local admin privileges. After downloading and decrypting the second-stage PowerShell script, the attacker performed a scan of the local network for the purpose of infecting additional machines on the network. Two additional hosts on the local were subsequently compromised by remotely executing a similar PowerShell command.

Threat quickly eliminated

The attacker’s total dwell time on the network was approximately 22 minutes, with lateral movement beyond Patient Zero occurring 10 minutes after initial compromise. Utilizing a combination of eSentire MDR for Endpoint which detected the malicious JavaScript file, machine learning from BlueSteel that detected the malicious PowerShell command, and eSentire MDR for Network which alerted on the suspicious web redirect, the attacker had no chance to reach their objective. eSentire was able to isolate the three compromised hosts and terminate the attackers command and control channel to the network.