Symantec: More malware operators moving in to exploit Follina

Meanwhile Microsoft still hasn't patched the fatal flaw

While enterprises are still waiting for Microsoft to issue a fix for the critical "Follina" vulnerability in Windows, yet more malware operators are moving in to exploit it.

Microsoft late last month acknowledged the remote code execution (RCE) vulnerability – tracked as CVE-2022-30190 – but has yet to deliver a patch for it. The company has outlined workarounds that can be used until a fix becomes available.

In the meantime, reports of active exploits of the flaw continue to surface. Analysts with Proofpoint's Threat Insight team earlier this month tweeted about a phishing campaign, possibly aligned with a nation-state targeting US and European Union agencies, which uses Follina. The Proofpoint researchers said the malicious spam messages were sent to fewer than 10 Proofpoint product users.

Then, this week, Proofpoint researchers detected another phishing campaign run by a group connected to the Qbot data-stealing and backdoor botnet that was using Follina to infect systems with its malware.

Now Symantec threat hunters say they also have detected other groups using the flaw to deliver payloads of malware. In one instance, the attackers are deploying the remote access trojan (RAT) AsyncRAT, which includes a valid digital signature. Other attackers are deploying information stealer malware as the payload onto a compromised system.

"Since the details of the vulnerability started surfacing online, attackers were quick to start taking advantage of the flaw to install their payloads," the researchers wrote in a blog post. "Symantec has observed attackers using a similar HTML file to that used in the initial attack. Multiple attackers are using a variety of payloads at the end of successful exploitation."

Follina is a RCE vulnerability in the Microsoft Support Diagnostic Tool (MSDT) that allows attackers to subvert the ms-msdt protocol handler process. Attackers can use a specially crafted Word document that loads a malicious HTML file through the application's remote template function, according to Symantec.

If exploited, the attacker can potentially perform such tasks as running arbitrary code, installing programs, viewing, changing or deleting data and creating new accounts. They also can load and execute PowerShell code within Windows and the vulnerability can additionally be exploited via the Rich Text Format (RTF) file format, the researchers wrote.

One of the problems is that attackers don't need to use macros, so they don't need to trick victims into enabling macros for the attack to work. The vulnerability is on all supported versions of Windows.

According to the Symantec researchers, when the AsyncRAT runs, it will check for analysis functions on the system and work to shut them down. It then collects information about the compromised system, such as hardware identification, the username, executed path and operating system information. The information is then sent to a command-and-control (C2) server and executes the commands from the C2 server on the infected machine.

The information stealer that is being deployed by some threat groups steals such information as cookies and saved login data from web browsers, including Microsoft Edge, Chrome and Firefox.

Threat hunters with cybersecurity vendor Kaspersky also have been tracking attacks using the Follina flaw, noting in a blog post this week that organizations in the US are particularly being targeted. Other countries under attack include Russia, Brazil and India, as well as some in Western Europe.

"We expect to see more Follina exploitation attempts to gain access to corporate resources, including for ransomware attacks and data breaches," they wrote. 

While bad actors are going hard to exploit the vulnerability, it has been known about since 2020, when an academic paper was published outlining the flaw. In April, the Shadow Chaser Group tweeted that it had reported its own take on the vulnerability to Microsoft. ®

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