PowerPoint Slide Show Files Exploited for RAT Distribution
A Microsoft Office vulnerability patched by Microsoft in April, after threat actors had been using it in live attacks, is being abused in a new manner to infect computers with a remote access Trojan, Trend Micro warns.
Tracked as CVE-2017-0199, the originally zero-day remote code execution vulnerability was previously abused in attacks leveraging malicious Rich Text File (RTF) documents, exploiting a flaw in Office’s Object Linking and Embedding (OLE) interface to deliver malware such as the DRIDEX banking Trojan.
In recently observed attacks, however, CVE-2017-0199 is being exploited using a new method where PowerPoint Slide Show is abused for malware delivery. The malicious document is delivered as attachment to a spear-phishing email attachment, and the security researchers suggest that, as part of the attack, a sender address masquerading as that of a business partner is being used.
The email message is supposedly an order request, but no business documents are attached to it. What is attached, however, is a malicious PowerPoint Show (PPSX file) that supposedly leverages CVE-2017-8570, a different Microsoft Office vulnerability (supposedly an error made by the toolkit developer).
Once the file has been executed, however, PowerPoint initializes the script moniker and runs the remote malicious payload via the PowerPoint Show animations feature. After the CVE-2017-0199 vulnerability is successfully exploited, it downloads a file called logo.doc, which is instead an XML file with JavaScript code.
The JavaScript runs a PowerShell command to download and execute RATMAN.EXE from its command and control (C&C) server. This file is a Trojanized version of the REMCOS legitimate and customizable remote access tool (RAT) that, once executed, provides the attacker with the possibility to run remote commands on the user’s system.
The tool can be used to download and execute commands on the infected machine, to log keystrokes and screen activity, and to record audio and video using the system’s microphone and webcam. The Trojanized tool uses an unknown .NET protector to add more protection and obfuscation to hinder analysis even more, and also leverages encrypted communication.
“Ultimately, the use of a new method of attack is a practical consideration; since most detection methods for CVE-2017-0199 focuses on the RTF method of attack, the use of a new vector—PPSX files—allows attackers to evade antivirus detection,” Trend Micro notes.
As always when the use of malicious documents delivered via spam email is involved, users should pay extra caution when opening them (the same applies to clicking on links in emails), even if they come from seemingly legitimate sources. Organizations should also implement mitigation techniques against phishing attacks, to avoid compromise.
“Users should also always patch their systems with the latest security updates. Given that Microsoft already addressed this vulnerability back in April, users with updated patches are safe from these attacks,” the security researchers also note.
Related: Microsoft Patches Office, IE Flaws Exploited in Attacks
