Since 2017, at least 11 state-sponsored threat groups have actively exploited a Microsoft zero-day issue that allows for abuse of Windows shortcut files to steal data and commit cyber espionage against organisations across multiple industries.
Threat analysts from Trend Micro's Trend Zero Day Initiative (ZDI) discovered roughly 1,000 malicious.lnk files that exploited the flaw, known as ZDI-CAN-25373, which allowed cyber criminals to execute concealed malicious commands on a victim's PC via customised shortcut files.
“By exploiting this vulnerability, an attacker can prepare a malicious .lnk file for delivery to a victim,” researchers at Trend Micro noted. “Upon examining the file using the Windows-provided user interface, the victim will not be able to tell that the file contains any malicious content.”
The malicious files delivered by cybercriminals include a variety of payloads, including the Lumma infostealer and the Remcos remote access Trojan (RAT), which expose organisations to data theft and cyber espionage.
State-sponsored outfits from North Korea, Iran, Russia, and China, as well as non-state actors, are among those behind the flaw attacks, which have affected organisations in the government, financial, telecommunications, military, and energy sectors across North America, Europe, Asia, South America, and Australia.
Additionally, 45% of attacks were carried out by North Korean players, with Iran, Russia, and China each accounting for approximately 18%. Some of the groups listed as attackers are Evil Corp, Kimsuky, Bitter, and Mustang Panda, among others.
According to Trend Micro, Microsoft has not fixed the flaw despite receiving a proof-of-concept exploit through Trend ZDI's bug bounty program. Trend Micro did not react to a follow-up request for comment on their flaw detection and submission timeline.
Microsoft's position remains that it will not be fixing the vulnerability described by Trend Micro at this time because it "does not meet the bar for immediate servicing under our severity classification guidelines," though the company "will consider addressing it in a future feature release," according to an email from a Microsoft spokesperson.
Meanwhile, Microsoft Defender can detect and block threat behaviour, as detailed by Trend Micro, and Microsoft's Windows Smart App Control prevents malicious files from being downloaded from the internet. Furthermore, Windows recognises shortcut (.lnk) files as potentially malicious file types, and the system will automatically display a warning if a user attempts to download one.
