According to a New York Times article ("Attack of the Zombie Computers Is Growing Threat") ShadowServer is "now tracking more than 400,000 infected machines and about 1,450 separate I.R.C. control systems, which are called Command & Control servers." Moreover, it states that:
Computer security experts warn that botnet programs are evolving faster than security firms can respond and have now come to represent a fundamental threat to the viability of the commercial Internet. The problem is being compounded, they say, because many Internet service providers are either ignoring or minimizing the problem.
The New York Times piece offers some general advice about how to protect your computer. I’ll give you some quick specifics for PCs, using free programs.
First, let’s see how exposed your computer is to the Net. Go to Shields Up!, click on "Proceed" at the bottom of the page, click on "File Sharing," then click on "All Service Ports." If your computer, doesn’t pass these tests you’ll want to take remedial action.
Third, if you don’t have antivirus software, download and install AVG Anti-Virus Free Edition. Scan for viruses.
Fourth, if you don’t have antispyware software, download and install Ad-Aware SE Personal. Scan for spyware. Update and run it periodically.
Fifth (for DSL/cable users), if you really want to be safe and you don’t have a hardware firewall, buy one and disable the IRC ports: 194 and 6660-7000.
Wasn’t that fun? Now, run Shields Up! again. Hopefully, all is well. If not, tweak.
Keep in mind that free program versions lack features of paid ones. Also keep in mind that suite programs that you pay for often offer variable protection for various functions, and, while a single program may cover all functions, you may be better off mixing and matching single-function programs that are very highly rated by PC Magazine, PC World, and similar publications, keeping in mind that programs from different vendors can interfere with each other and experimentation may be needed to find the right mix.
Source: Markoff, John. "Attack of the Zombie Computers Is Growing Threat." The New York Times, 7 January 2006, 1, 16.