The recent arrests of three men in The Netherlands who allegedly controlled a network of more than 100,000 compromised computers will not likely curtail the criminal economy surrounding so-called bot nets, security experts said this week. The arrests, announced last week by The Netherlands' National Prosecution Service, follow the August capture of two men - one from Turkey and the other from Morocco - suspected of creating and spreading the Zotob worm, a program that also compromised computers in order to create a bot net.
Security experts applauded the successful investigations but remained pragmatic about the impact the arrests will have on the increasing use of bot nets as a means to facilitate online crime.
"We hope that it will cut down the activity of some of the bot net herders, but I am not too hopeful," said Mikko Hyppönen, chief research officer for antivirus firm F-Secure. "If creating these networks is still profitable, then they will still do it, and probably just be more careful."
The arrests, announced last Friday, are the latest counterstrike against criminals who use bot nets to attack corporate networks, capture sensitive and financial information and send bulk email messages such as spam and phishing attacks. In August, the FBI and Microsoft helped authorities in Turkey and Morocco track down two men suspected of creating and spreading the Zotob worm--a program that consisted of bot software modified to exploit a flaw in Windows 2000. In May, the US Federal Trade Commission kicked off an initiative to reduce the number of botnets able to send out spam and phishing email messages.
The latest arrest in The Netherlands was the result of an investigation by that nation's National High Tech Crime Center, the National Prosecution Service, and Computer Emergency Response Team of the Dutch government as well as several Internet providers. The arrest should be somewhat heartening for the European Union as computer systems hosted in the EU comprise the largest block of compromised systems in the world, according to data collected in the first half of 2005 by Prolexic Technologies, which has built a business by helping its clients deal with the denial-of-service attacks leveled by the controllers of some botnets.
Such systems are used for a variety of criminal enterprises, said Barrett Lyon, chief technology officer for Prolexic.
"We saw the extortion racket take off first, but now it is a mixture," Lyon said. "You are seeing extortion; you are seeing competitive-advantage attacks; and you are seeing censoring attacks."
Some websites have had to deal with denial-of-service attacks by bot nets because attackers believed the site to hold a certain point of view, he said.
The three Dutch suspects allegedly used the 100,000 computers in the bot net to take down a US company's website with a denial-of-service attack in an attempt to extort money from the company, the National Prosecution Service said in its statement. In addition, the bot herders -the name used by security researchers to describe those who control botnets - likely captured the log-in credentials to victims' bank accounts.
Online criminals' use of botnets to send spam and phishing email messages convinced the US Federal Trade Commission to kick off Operation Spam Zombies, a campaign focused on educating Internet service providers (ISPs) about what they could do to clean up the amount of compromised computers, also called zombies, on their networks.
"This particular project targets ISPs because we think they have a large ability to improve the situation where others could not," said Markus Heyder, a legal adviser in the FTC's Division of International Consumer Protection and the coordinator for the project."They are in the best position to understand the technology and secure their systems better than they are doing right now."
The FTC does not yet have data on whether its initiative has produced results, Heyder said.
While the recent successes by law enforcement have garnered some attention, the botnet problem will not likely be easily dismissed, security experts said in interviews this week.
For one, bot software that infects vulnerable computers has evolved and now typically consists of modular architectures into which new functionality can be plugged quickly and easily. For example, the latest exploits for Microsoft's operating system are incorporated into such bot software in weeks, if not days.
The three Dutch suspects are alleged to have used a customized version of the publicly available SDBot software to build their network of compromised computers. The software, dubbed W32.Toxbot by antivirus firms, records keystrokes and sends the information back to the attackers.
Such customization is standard, said Joe Stewart, a senior threat researcher for security firm LURHQ.
"Every group seems to take code and adapt it to their purposes," Stewart said.
Bot software is also taking its cues from the world of peer-to-peer networking. The latest software uses peer-to-peer technology to make it harder to shut down the network and to hide the location of the attacker, said Prolexic's Lyon.
Such innovations will likely continue because the crimes still reward the savvy bot programmer, Lyon said. In one case, for example, Prolexic was able to confirm that a group of bot herders had received more than $8m from various extortion schemes. Generally, bot herders use their networks to threaten companies with a denial-of-service attack unless they pay. However, companies that do pay frequently find the attackers return to threaten them again and again.
"Eight million (dollars) is quite an incentive," Lyon said. "It also buys you a lot of new features for your bots from programmers."
Internet service providers have increasingly focused at heading off the problem by notifying customers on their networks that likely have computers compromised by bot software.
America Online, a division of Time Warner, has had to develop technology to battle botnets, said Andrew Weinstein, a spokesman for Internet giant.
"We tend to notice DOS attacks and be able to respond to them faster than anyone," he said. "Technology has helped mitigate the most severe affects of DDOS attacks."
Not all the efforts of ISPs work well, however. Some providers block Internet Relay Chat (IRC), a common protocol for controlling botnets, but many of today's bots use nonstandard channels, or ports, to communicate, said LURHQ's Stewart. I
It's an arms race in which both the Internet service providers and law enforcement have to work harder to get ahead, he said.
"People making money off of it are not going to stop because someone else in a different country got arrested or because a large botnet got taken down," Stewart said. "Hopefully, as law enforcement gets more clued in to how botnnets operate, we will get a critical mass where it acts as an actual deterrent to these people."
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