Imperfect Storm aids spammers

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Anti-spam sites under spam fire

For 24 hours in mid-January, stock-fraud investigation site StockPatrol disappeared from the internet, overwhelmed by a massive flood of web requests coming from thousands of sources.

The attack came after the site wrote a handful of reports investigating and condemning the practice of pump-and-dump stock spam campaigns. No fewer than three botnets targeted StockPatrol, as well as another anti-spam site, and at least five command-and-control servers associated with a different virus, Warezov, according to an analysis released last week.

"StockPatrol.com was the victim of a cyberspace assault that evidently was calculated to disable our site and make our reports inaccessible," read a statement posted on 17 January. "In this instance the attack was massive."

At the heart of the attack was a single program designed specifically to co-opt victims' computers to aid in sending stock-touting email messages and to participate in denial-of-service attacks - Storm Worm. The program appeared on 19 January and compromised systems by luring their users into opening the attachments of messages with subject lines regarding current news events - including violent storms in Europe. Because the program does not propagate on its own, the name adopted from its subject lines is a misnomer - the Storm Worm is actually a Trojan horse.

The program highlights a number of changes in the techniques used by criminal internet groups. The Storm Worm spreads in fairly large, but controlled, bursts of email through previously compromised computers. Each burst typically sends out a custom variant, causing headaches for anti-virus makers. (More on this in part two of this series.)

"The outbreak occurred in smaller waves, much in the same way the Warezov virus appeared," said Paul Wood, senior analyst with MessageLabs. "Each of the waves appears with a dozen different variants of the virus. They don't just carry on and on. They are spammed out, then they wait a bit because the antivirus companies create signatures, and then they spam out a new set of variants."

At one point, the creators of the Storm program sent out a new set of variants daily, forcing anti-virus firms into a running battle to protect their users.

"Every day, it has been a new set of subject lines and new tactics to get people to open these," Allysa Myers, virus research engineer for security software maker McAfee, said in late January. "They have had mass seedings of new variants every day this week."

Highlighting another trend, botnets created with the program use peer-to-peer communication to make shutting down the illicit networks much more difficult. Typically, botnets last no more than a day after their command-and-control server is identified. The peer-to-peer component of the Storm Worm enables its botnets to reconstitute themselves after the central server is taken down.

"In the traditional botnet, if you cut off the head, you kill the beast," said Dean Turner, senior manager of development for security firm Symantec, the owner of SecurityFocus. "We speculate that, as more command-and-control servers get identified by ISPs, you will see more and more of these botnets go to peer-to-peer.

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For all that, the techniques are not new, said Joe Stewart, senior security researcher with SecureWorks. Stewart penned last week's analysis connecting Storm Worm to the denial-of-service attacks.

"I don't think Storm is any large step forward," Stewart said. "Everything it does, we have seen in one form or another before. Someone has sat down and decided what they wanted and built it out of technology that is already out there."

Attacks on rival spam gangs and anti-spam sites are not that unique either. Yet, the people who are propagating the Storm Worm have not been shy about the attacks, Stewart said. Attacks were also leveled at anti-spam site SpamNation, which maintains a list of the latest stock touts, and money transfer site CapitalCollect.

"The spam war is escalating to new levels," wrote Stewart in an analysis posted on SecureWorks' blog. In the analysis, he pointed to the successful attack on anti-spam firm Blue Security as possibly emboldening the spammers. That company folded after the May 2006 assault.

"With no repercussions from that attack, or even older attacks which shut down certain DNS blacklists, it seems that more spammers are willing and able to attack anyone who threatens their profit potential," he said.

That includes rivals. The Storm Worm botnets attacked five websites associated with a competing program, Warezov. The reason is clear, said SpamNation's anonymous editor: Spammers that are about to pump up one stock don't want their competitor blunting the effect or confuse the potential marks by pumping a different stock.

"It shouldn't come as any surprise to learn that spammers are fighting amongst themselves," the editor wrote in a recent post. "The fiercest competitors of any organism are other members of its own species, which compete for the same food and resources that it needs to survive and breed."

Warfare among malware writers is standard fare. The author of variants of the Netsky virus often taunted the writers of MyDoom and Bagle. In 2005, the groups behind different variants of the Zotob virus attempted to attack and control the machines compromised by their competitors.

In this case, the battle between the two groups pits gangs of two nationalities against each other, according to SecureWorks' Stewart. All signs indicate that Warezov is used by attackers based in China, Stewart said. Botnets created with the Trojan horse program take commands from servers in China and the code uses the MEW packer, a compression utility favoured by the Chinese because it has releases in Mandarin.

The Storm Worm on the other hand uses packers favored by Russian groups and has connections to servers based in Russia, he said.

While the attacks have moved beyond a war of egos, they remain bold just the same. And without much luck in hunting down the people behind the bot nets, it may not get better, Stewart said.

"It seems like they feel they're in a position where they are untouchable," he said.

This article originally appeared in Security Focus.