Slapper Worm brought to heel
As variants appear
Two fresh variants of the Slapper worm, which spreads through Linux machines by exploiting a well-known flaw in OpenSSL libraries, have been sighted this week.
Slapper.B (or Cinik) differs from the original worm in using port 1978, instead of port 2002, to control infect machines. The filename of the worm has been changed to "cinik.c".
The worm also has 'backup functionality', of sorts. If the worm is removed from the host, then it tries and download a copy of the worm from a page on a Romanian web site. Although this virus page has now been deleted, this hasn't spotted the worm spreading, modestly, across infected Linux servers.
Another variant of Slapper, Slapper.C (or Unlock), uses port 4156 instead of port 2002 in its infection routine. The filename used in this variant is "unlock.c".
Both variants, like the original, take advantage of the same vulnerability in Open SSL libraries, which dates back to last month, to infect Linux machines running Apache web server with OpenSSL enabled. This is a particular concern given the widespread use of this configuration in numerous ecommerce operations.
In addition, the worm contains code to create a peer-to-peer attack network, where infected machines can remotely be instructed to launch Distributed Denial of Service attacks.
Most potential targets have now been patched to prevent infection, as a result of which the damaging worm has now been brought under control. Linux admins who haven't done already are strongly advised to update to OpenSSL version 0.96d or older to guard their Apache servers against potential infection.
Infections due to Slapper thankfully ran at far lower rates to that caused by worms that infected Windows machines, such as Nimda, recorded last year.
In related news, reports that a 21-year old Ukrainian was arrested on suspicion of authoring the Slapper worm earlier this week have been discounted. ISS has retreated from its earlier reported assertions that an arrest had been made while AV experts gathered in New Orleans for this week's Virus Bulletin Conference are unable to confirm the arrest. ®