Rootkits--malicious software that operates in a stealth fashion by hiding its files, processes and registry keys--have grown over the past five years from 27 components to 2,400, according to McAfee's Rootkits Part 2: A Technical Primer (PDF).
"The trend is it used to be rootkit A was used, but now it's different components in different rootkit malware," said Dave Marcus, security researcher and communications manager for McAfee Avert Labs. "Now, there are more ways attackers can use these components to hide their malware."
Attackers use rootkits to hide their malicious software, which can range from spyware to keylogger software that can steal sensitive information from users' computers. The rootkits can then be used to create a hidden directory or folder designed to keep it out of view from a user's operating system and security software.
However, more security firms are, Marcus said. Some of the techniques used to detect rootkits include scanning active memory on users' computers in a number of locations on the system.
Security firms are finding that by locating malicious software, such as a Trojan horse, their software is not only eliminating the Trojan but also the rootkit, Marcus said.
That may explain the decrease in the number of rootkits found in malicious software over the past year. From the first quarter of 2006 to the first quarter of this year, the number declined by 15 percent, Marcus noted.