Malware Installation Using CHM Files

A recent spam campaign is delivering trojans via malicious Compiled HTML (CHM) files. The current phishing campaign, used to lure users into downloading the trojan malware, is using WhatsApp, a popular messaging service as a cover for its malicious intent.

Threat ID:: CC-1691
Category:: Trojan
Threat Severity:: Medium
Threat Vector:: Phishing
Published:: 10 October 2017 12:00 AM

Report a cyber attack: call 0300 303 5222 or email [email protected]

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Summary

Affected platforms

The following platforms are known to be affected:

Microsoft Windows

Windows - All Versions

Threat details

CHM usually consist of HTML pages, indexing, and other navigation tools. Their main purpose is to provide help to a user, however cyber-criminals are using them to execute malicious code via PowerShell commands.

When the link is clicked, it will download a zip file, which contains the malicious CHM file. With this spam campaign, the attacker used a technique first seen in 2005, which involves modifying a genuine transmission control protocol (TCP) IPv4 help file into one that contains an object linking and embedding control extension (OCX), which launches a PowerShell command when triggered. When the command is run, it will launch a script to download the malicious files onto the user’s system. The files are placed in a created folder named paladium, under C:\ProgramData. A task is also scheduled to launch the malicious files every one and a half hours and download new versions of the Trojan.

Threat updates

Date	Update
4 Jan 2018	Malicious CHM files have been used to download the Bancos Banking Trojan.

Remediation advice

To prevent and detect a Trojan 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, antivirus and other security products are kept up to date. All day to day computer activities such as email and internet are performed using non-administrative accounts. Strong password policies are in place and password reuse is discouraged. Network, proxy and firewall logs should be monitored for suspicious activity. User accounts accessed from infected machines should be reset on a clean computer

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, antivirus and other security products are kept up to date.
All day to day computer activities such as email and internet are performed using non-administrative accounts.
Strong password policies are in place and password reuse is discouraged.
Network, proxy and firewall logs should be monitored for suspicious activity.
User accounts accessed from infected machines should be reset on a clean computer

Last edited: 17 February 2020 11:34 am