Writing in the latest Windows Secrets newsletter, security expert Susan Bradley describes the latest Windows malware (malevolent software) floating around the Internet. Many well-known and popular web sites have become infected and they spread the infection to any Windows PC that visits the site using Internet Explorer and some out-of-date software.
I didn't see any genealogy-related web sites mentioned in Susan's list but I'd still suggest caution. Susan lists ColdwellBanker.com, Variety.com, and Tennis.com as web sites that are infected or have been infected in the past.
You can read all the details in Susan's article at http://windowssecrets.com/2009/06/11/01-Big-name-sites-spread-latest-malware-infections/#story1.
NOTE: That site seems to be busy this morning, it took three attempts before it would open up for me and then it was very, very slow. I suspect that lots of people want to read that article today.
Susan also describes the process to see if your Windows PC is infected and, if so, she also tells how to remove the problem.
Luckily, it is easy to prevent the problem: don't use Windows Explorer. Both Firefox and Opera are safe and do not have this problem, nor do the Linux or Macintosh operating systems.