Twitter says its spam levels have dropped significantly to a new low of 1 percent of all tweets -- a major decrease from the level of nearly 11 percent in August 2009.

Spam has been steadily declining as of December, from about 4 percent to the current volume of 1 percent as of February, according to a graphic on spam traffic posted by Twitter. Spammy tweets averaged in the 5 to 6 percent range most of last year, but started to dwindle in the fall, with occasional spikes, according to the data.

"We're constantly battling against spam to improve the Twitter experience, and we're happy to report that it's working," said Twitter's chief scientist, Abdur Chowdhury, in a blog post yesterday. "While the battle will never be over, we're doing well on the front lines."

But still a hefty chunk of Twitter profiles are spammers. Errata Security, which runs an experimental service for detecting Twitter spam and malware called TwiGUARD, today analyzed the profiles of 160,000 active Twitter users and found that 10 percent of them were spammers. David Maynor, CTO of Errata Security, says TwiGUARD uses a scoring system to identify spammers based on certain behaviors.

Twitter earlier this month added a new service that detects malicious URLs; the service will ultimately scan all URLs before they hit the Twitter feed, but initially is doing so only for URLs sent via Twitter direct messages [DMs] and email notifications about DMs.

The social network has a "report for spam" link on Twitter profile pages, which alerts Twitter about a sketchy account and blocks it from following or replying to the user who reports it, Chowdbury says. And users also can tweet @spam to report any spam problems.

Spam started becoming a big problem on Twitter during what security experts at Barracuda Labs call the "Red Carpet Era" of the social network -- the period during November 2008 to April 2009 when a wave of celebrities joined the microblogging site. One in eight Twitter accounts was identified as malicious, suspicious, or suspended last year, according to Barracuda.

Today 3 to 4 percent of Twitter accounts are detected as malicious, according to Paul Judge, chief research officer at Barracuda. Judge says Barracuda sees about 9 to 10 percent of all Twitter accounts conducting some form of malicious activity.

Aside from TwiGUARD, another free service for users to report Twitter spam was recently launched: Spamdetector, a spam-filtering service that flags spammers for Twitter, which then removes those accounts.

"I think Twitter has done a lot to curb malicious use, but with a financial motivation, attackers will evolve their craft," Errata Security's Maynor says. "There isn't much Twitter can do besides walk a tightrope between being an open community and requiring more stringent validation checks when registering accounts."

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