Sober’s success caused by antivirus weakness
The longevity of the current Sober worm may be largely due to a new technique it uses to evade virus scans, according to antivirus firm Kaspersky Labs.
The worm, variously labelled Sober.P, Sober.S, Sober.O and Sober.V by different companies, continues to circulate in large amounts, making up 84% of all virus traffic as of Monday, according to Sophos. While researchers have attributed its success to the fact that it circulates in both English and German, and to its use of free World Cup tickets as a lure to users, social engineering is only part of the equation, Kaspersky says.
The new variant used a refined mechanism for blocking input/output access to its files by other programs, says Kaspersky senior research engineer Roel Schouwenberg in an alert posted this week. Previous variants used a similar technique, but didn’t succeed in blocking programs running in the System account.
Sober.P does what the others didn’t do and blocked the System account as well, Schouwenberg says. That meant no other programs, including antivirus scanners, could detect Sober.P while it was resident in memory, he says.