Major Linux security glitch lets hackers in at Claranet

10-minute swoop to close new hole

A major security vulnerability in the Linux kernel, which was revealed on Sunday, has claimed its first confirmed UK victim in business ISP Claranet.

Hackers used a bug in the sys_vmsplice kernel call, which handles virtual memory management, to gain root privileges and replace Claranet customers' index.html files with the hacker's calling card.

The exploit was noticed at about 6pm on Tuesday.

Claranet said: "Malicious activity related to the vulnerability was detected on Claranet's shared hosting platform. Within 10 minutes Claranet contained and halted the malicious activity, and locked down the platform to prevent further damage.

"The shared hosting platform was fully patched with the vendor's updates by 10am on Wednesday. Less than one per cent of the total web sites hosted on the Claranet platform were affected and all were restored to their original states by 1pm on Wednesday 13 February."

The (potentially tricky) hacking process was dumbed down by the publication of exploit code earlier this week, Linux-Watch notes.

Security notification firm Secunia reports that switching to either version 2.6.23.16 or 2.6.24.2 of the Linux kernel guards against attack. Hotfixes designed to plug the vulnerability short of upgrading the kernel have also been released.

The affected system call first appeared in version 2.6.17 of the Linux kernel, but wasn't left open to exploit until changes were made with the 2.6.23 version.

Linux vendors are working on a permanent fix for the problem. Claranet emphasised that it keeps a close eye on announcements of new vulnerabilities and acts swiftly to patch them. ®