Microsoft Corp. security researchers are warning about a new generation of powerful system-monitoring programs, or "rootkits," that are almost impossible to detect using current security products and could pose a serious risk to corporations and individuals.
The researchers discussed the growing threat posed by kernel rootkits at a session at the RSA Security Conference in San Francisco this week. The malicious snooping programs are becoming more common and could soon be used to create a new generation of mass-distributed spyware and worms.
With names like "Hacker Defender," "FU" and "Vanquish," the programs are the latest generation of remote system-monitoring software that has been around for years, according to Mike Danseglio and Kurt Dillard, both of Microsoft's Security Solutions Group.
The programs are used by malicious hackers to control, attack or ferret information from systems on which the software has been installed, typically without the owner's knowledge, either by a virus or after a successful hack of the computer's defenses, they said. Once installed, many rootkits run quietly in the background but can easily be spotted by looking for memory processes that are running on the infected system, monitoring outbound communications from the machine, or checking for newly installed programs.
However, kernel rootkits that modify the kernel component of an operating system are becoming more common. Rootkit authors are also making huge strides in their ability to hide their creations, said Danseglio.
In particular, some newer rootkits are able to intercept queries or "system calls" that are passed to the kernel and filter out queries generated by the rootkit software. The result is that typical signs that a program is running, such as an executable file name, a named process that uses some of the computer's memory, or configuration settings in the operating system's registry, are invisible to administrators and to detection tools, said Danseglio.
The increasingly sophisticated rootkits and the speed with which techniques are migrating from rootkits to spyware and viruses may be the result of influence from organized online criminal groups that value stealthy, invasive software, said Dillard
One rootkit, called Hacker Defender, released about a year ago, even uses encryption to protect outbound communications and can piggyback on commonly used ports such as TCP Port 135 to communicate with the outside world without interrupting other applications that use that port, he said.
The kernel rootkits are invisible to many detection tools, including antivirus, host and network intrusion-detection sensors and antispyware products, the researchers said. In fact, some of the most powerful tools for detecting the rootkits are designed by rootkit authors, not security companies, they said.
There are few strategies for detecting kernel rootkits on an infected system, especially because each rootkit behaves differently and uses different strategies to hide itself.
It is sometimes possible to spot kernel rootkits by examining infected systems from another machine on a network, said Dillard. Another strategy to spot kernel rootkits is to use Windows PE, a stripped-down version of the Windows XP operating system that can be run from a CD-ROM, to boot a computer and then compare the profile of the clean operating system to the infected system, according to Dillard and Danseglio.
Microsoft researchers have developed a tool called Strider GhostBuster that can detect rootkits by comparing clean and suspect versions of Windows and looking for differences that may indicate that a kernel rootkit is running, according to a paper published by Microsoft Research.
The only reliable way to remove kernel rootkits is to completely erase an infected hard drive and reinstall the operating system from scratch, Danseglio said.
Although rootkits are not unique to Windows, the popular operating system is a rich target and makes it easy for malicious hackers to disguise the presence of such programs, according to Jonathan Levin of Symantec Corp.'s @stake division, who attended the presentation at the RSA conference.
The operating system's powerful application programming interfaces make it easy to mask behaviors on the system. Microsoft's Internet Explorer Web browser is also a frequent avenue for malicious hackers, viruses and worms that could drop a rootkit on a vulnerable Windows system, Levin said.
Better tools could be built to detect the current crop of kernel rootkits. However, rootkit authors are adept at spotting new detection techniques and modifying their programs to slip around them, Danseglio said. "These people are smart. They're very smart," he said.