New Delphi-based Packer Used to Avoid AV Detection

A new executable packer has been observed being used by several well-known malware variants, including LokiBot, Remcos and AZORult, to avoid classification or detection by anti-virus and other security solutions.

Threat ID:: CC-2685
Category:
Threat Severity:: Low
Threat Vector:: Email spam
Published:: 26 September 2018 12:00 AM

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Summary

Affected platforms

The following platforms are known to be affected:

Microsoft Windows

Microsoft Windows - All versions

Threat details

The packer is written in Delphi, a programming language that can be used to rapidly create native applications for most popular computing platforms. Many Delphi applications make use of standard Windows API functionality, with some malware authors including default libraries to prevent analysis. The packer uses several of these APIs to verify it is not installed on a virtual machine. The GetForegroundWindow, GetCursorPos and Sleep APIs are used to check for user activity; while the GetLastInputInfo and GetTickCount APIs check the system idle state.

Payloads using this packer will be split into multiple encrypted binary sections within the new file in order to prevent detection by AV applications. When executed, the packer uses a hard-coded ID to generate an XOR key, which it will then use to locate and decrypt the payload sections before reassembling and executing it.

At the time of publication, all payloads using this packer have been distributed via spam campaigns, although it is possible other delivery vectors are being used.

Remediation advice

To prevent and detect an infection, ensure that:

Remediation steps

Type	Step
	A robust program of education and awareness training is delivered to users to ensure they don’t open attachments or follow links within unsolicited emails. All operating systems, anti-virus and other security products are kept up-to-date. Regular anti-virus and security scans are performed on your organisation’s estate. All day-to-day computer activities such as email and internet are performed using non-administrative accounts. Strong password policies are in place. Network, proxy and firewall logs should be monitored for suspicious activity. User accounts accessed from affected devices should be reset on a clean computer. Your organisation adopts a holistic all-round approach to Cyber Security as advocated by the 10 Steps to Cyber Security.

Type

Step

A robust program of education and awareness training is delivered to users to ensure they don’t open attachments or follow links within unsolicited emails.
All operating systems, anti-virus and other security products are kept up-to-date.
Regular anti-virus and security scans are performed on your organisation’s estate.
All day-to-day computer activities such as email and internet are performed using non-administrative accounts.
Strong password policies are in place.
Network, proxy and firewall logs should be monitored for suspicious activity.
User accounts accessed from affected devices should be reset on a clean computer.
Your organisation adopts a holistic all-round approach to Cyber Security as advocated by the 10 Steps to Cyber Security.

Last edited: 17 February 2020 12:50 pm