Attackers have managed to bypass a security patch that Microsoft issued last week to address the recently discovered Sandworm vulnerability in Windows, prompting the company to issue another advisory this week, warning users of the new threat.
All supported versions of Windows, except Windows server 2003, continue to be vulnerable to attacks that attempt to exploit the vulnerability through rogue PowerPoint attachments, Microsoft noted earlier this week.
“An attacker who successfully exploited the vulnerability could gain the same user rights as the current user,” Microsoft warned. The company issued a temporary Fix It patch for mitigating exposure to the threat and encouraged users to apply it immediately.
The Sandworm vulnerability refers to a Windows packager zero-day flaw that basically gives attackers a way to take complete remote control of an infected system. Attackers typically have exploited the flaw using malicious PowerPoint files sent as innocuous attachments to unsuspecting users. When an infected PowerPoint file is opened, it drops a malicious payload on the system.
Russian cyber espionage gang Sandworm has used the exploit in numerous attacks against NATO, the Ukrainian government, and various targets in the US since 2013.
Microsoft last week issued a patch (MS14-060) to address the flaw, which exists in the Object Linking and Embedding (OLE) code within Windows.
However, several security vendors have reported seeing continued attacks seeking to exploit the same vulnerability in the days since Microsoft issued the patch.
In a blog post, Symantec said it has seen at least two groups of attackers that are continuing to take advantage of the Sandworm flaw by using an exploit that deftly sidesteps the Microsoft patch.
As with previous exploits, attackers are still using malicious PowerPoint documents to try and trick users into downloading malware on their systems, Symantec noted.
The new attacks are being used to deliver at least two different malicious payloads to victims. Symantec identified one of the payloads as Trojan.Taidoor and the other as Backdoor.Darkmoon or Poison Ivy.
The group using Taidoor has been around since at least 2008 and has a track record of exploiting new zero-day flaws, Symantec said. The Darkmoon variant, meanwhile, appears to have been ready for use several weeks before Microsoft disclosed the Sandworm vulnerability last week, Symantec added.
According to Trend Micro, with the new exploits, attackers are embedding the malicious files directly in the OLE object. So when a user opens an infected PowerPoint file, the malware is dropped directly on the system, instead of from a remote location.
“One advantage of this approach is that it will not require the computer to connect to the download location, thus preventing any detection from the Network Intrusion Prevention System (NIPS),” Trend Micro threat analyst Ronnie Giagone wrote on Trend Micro’s Security Intelligence blog.
McAfee security researcher Haifei Li said that Microsoft’s original patch for the Sandworm vulnerability might not have been “robust enough” to stop attackers from exploiting it. “In other words, attackers might still be able to exploit the vulnerability even after the patch is applied. Users who have installed the official patch are still at risk,” Li wrote on McAfee’s blog.
Users who are concerned about the threat should apply the Microsoft Fix It from this week’s advisory or apply the workarounds contained in the original MS14-060 bulletin from last week, Li said.