Mozilla's head of security is to step down at the end of the year.

Window Snyder, who holds the official title 'chief security something-or-other', admitted she has resigned from her position in a blog.

Snyder hasn't yet revealed what her next step will be. She joined Mozilla in 2006 after working as a security strategist for Microsoft. She is currently in charge of improving security in the Firefox web browser and other Mozilla projects.

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Security has become more important for Mozilla as its Firefox browser has gained more users, making it a more attractive target for malicious hackers. Just last week it was being targeted by a new Trojan that tries to steal online banking passwords, according to security company BitDefender.

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"It's impossible to build a perfectly secure browser," Snyder previously told Computerworld. "That's not the goal. The goal is to build the safest browser we can. It's an ongoing process. It's not a goal where we'll say, 'OK, we're done.'"

In her blog, Snyder said she was leaving Mozilla's security in capable hands, naming several colleagues who will assume her duties.

See also: Beta version of Thunderbird 3.0 released