I found these videos very informative and very well made. They are made by/for "watchguard", but ignore that, this is useful info for everyone. If you're interested in security, "hacking" and info about malware, what it does, how and why, i recommend you to watch these, all 8. They are at times much more detailed than usual, almost a lesson in how to create and use malware. I knew all this already, but these are so well made that i watched them anyway. If you're going to watch all these, it will take almost 2 hours, but imo 2 hours so well spent that i'll tell certain IT-people at work to watch these also, on paid time. I downloaded them all (gives significantly better resolution) and ended up with a total 450 MB.
Video 1: Botnets Part 1. Shows what they are, do, how, and how to set one up. (16m:16s)
http://www.watchguard.com/education/video/play.asp?vid=botnets1
Video 2: Botnets Part 2, continued. (13m:10s)
http://www.watchguard.com/education/video/play.asp?vid=botnets2
Video 3: Botnets Part 3, how to protect your network. (12m:52s)
http://www.watchguard.com/education/video/play.asp?vid=botnets3
Video 4: Botnet Source Code. More in detail how this works. (13m:52s)
http://www.watchguard.com/education/video/play.asp?vid=botnets1_overachievers
Video 5: Drive-By Download. Infecting your computer by simply viewing a website. (12m:03s)
http://www.watchguard.com/education/video/play.asp?vid=dbd-cubecast
Video 6: Rootkits Part 1. Explanation of rootkits, demo of what they can do and how. (12m:21s)
http://www.watchguard.com/education/video/play.asp?vid=root1-cubecast
Video 7: Rootkits Part 2. Continued. (8m:55s)
http://www.watchguard.com/education/video/play.asp?vid=root2-cubecast
Video 8: Rootkits Part 3. More advanced. (16m:00s)
http://www.watchguard.com/education/video/play.asp?vid=root3-cubecast