There were lots of great security topics in 2009 — if by great, you mean, “scary.” Fortunately, TechRepublic’s Security bloggers Michael Kassner and Chad Perrin were busy taking in-depth looks at how the bad guys are working, the technology used to combat them, and the potential consequences to your own systems and networks.

Below is a short list of the best reports, tips, and warnings from 2009 based on a combination of views, discussions, and votes. Review the list and let us know what you thought the big stories were in 2009 — and what you are going to be watching for in 2010.

#1 Microsoft may be Firefox’s worst vulnerability

Chad Perrin reported on Microsoft’s surprise move to quietly install what he called a massive security vulnerability in Firefox without informing the user. TechRepublic members were not amused! Chad offered some tips on how to undo the damage. Read the original post.

#2 Conficker.C: April Fools or maybe not

Previous versions of the Conficker malware had already plagued users for months, and not patching systems threatened to make things even worse. On the eve of an expected variant striking, Michael Kassner dissected the Conficker threat and armed readers with as much knowledge as possible. Read the original post.

#3 Nigerian 419 scammers: What you didn’t know

Michael Kassner dove into the shadowy world of people behind the con of Nigerian email-phishing scams. What he found was a weird underworld culture of big money, folk songs, and voodoo. Who knew!? Read the original post.

#4 10 tips for personal security when you leave an employer

Unfortunately in 2009, many companies continued to bleed jobs, and all that employee transition opened up gaps in security, not only for organizations, but also for departing individuals. Chad Perrin tackled the issue with one of his most popular pieces — tips on how to safeguard your personal security when leaving an employer. Read the original post.

#5 Online banking: How safe is it?

Online banking is nearly ubiquitous, so it’s a big concern for a lot of people. After reviewing an MIT report on the subject, Michael Kassner began investigating crimeware and offered mitigations for the security-conscious. Read the original post.

#6 Why do people write viruses?

Chad Perrin delivered his take on the kinds of people who write viruses and malware and what really motivates them. Read the original post.