PoC code uses super-critical Windows bug to crash PCs
Crash code real, but Sabu worm rumours ... not so much
Security watchers have discovered proof-of-concept code that attempts to exploit a high-risk Windows security hole, causing computers to crash.
The exploit attacks a RDP (Remote Desktop Protocol) flaw patched by Microsoft on Tuesday. Redmond's security staffers warned at the time that the critical update (MS12-020) was of a type hackers were likely to latch onto, warning that exploits were likely to follow within 30 days.
The discovery of proof-of-concept code on a Chinese website less than 72 hours later came as no great surprise. Security firms warned that worse is likely to follow. The vulnerability might easily be exploited to create a worm that spreads automatically between vulnerable computers.
"The hackers worked quickly on this particular vulnerability and we've already seen attempts to exploit the flaw which exists in a part of Windows called the Remote Desktop Protocol (RDP)," said Graham Cluley, senior technology consultant at Sophos. "Affected Windows computers will 'blue screen', but I wouldn't be surprised if whoever is writing this code tries to develop the attack further to produce a fast spreading internet worm."
In related news, a supposed Python script for a worm that exploits the RDP exploit has appeared online. Sophos says the claim is a hoax and no such worm exists, at least for now.
"It references a Python module that doesn't exist (FreeRDP), and claims to be written by email@example.com, an obvious reference to the high profile Anonymous hacker who was recently revealed to have been secretly working for the FBI for months," Cluley explains.
RDP is disabled by default on Windows, but often activated in corporate environments. The utility of the service means it is commonly allowed through firewalls. In addition, no authentication would be needed to hack into many vulnerable hosts, factors that explain the unusually high profile of warnings given to the bug.
Enterprises are advised to apply patches quickly, where possible, or at minimum to allow Microsoft's suggested exploit mitigation strategies. Defensive measures involve activating the Remote Desktop’s Network Level Authentication (NLA) to require authentication before a remote desktop session is established, as explained by Microsoft here. ®