Since the microblogging service exploded in popularity just a few short years ago, Twitter's most egregious problem has been spam. Type 'iPad' in a tweet, and expect a deluge of twitterbots @replying you with fake offers of $99 discount tablets.

Twitter took a new step in its fight against spammers on Thursday, filing a lawsuit in a San Francisco federal court against companies that create tools to automate posting to and following people on Twitter.

The suit names five defendants: TweetAttacks, TweetAdder, TweetBuddy, James Lucero and Garland Harris – which Twitter claims are the biggest offenders in the Twitter spamming racket – arguing they are the arms dealers to those who fill the service with fake profiles and unwanted @ messages.

"By shutting down tool providers, we will prevent other spammers from having these services at their disposal," Twitter said in a company blog post. "With this suit, we’re going straight to the source."

Twitter's hardly the first tech company to go after spammers – a number of other major Internet companies have filed federal lawsuits in the fight against spammers. Recently, Facebook filed two lawsuits against Adscend Media, a firm that Facebook alleges is intent on spreading Facebook spam through deceptive practices, or "clickjacking." Google has sued in similar situations involving online pharmacy scams and other online scammers.

As for going after those who provide tools to automate spamming, Craigslist has had success. The classifed ads site sued spammers of its website in Federal court in 2009, and in one case won an injunction and $200,000.

So filing suit against the biggest players in the Twitter spam world sets the agenda for any other would-be spammers out there. If another tweet spam outfit pops up on Twitter's radar, the company can point the would-be spammers to Twitter's past legal actions, as well as the Craigslist win that sets precedent. It's no guarantee that Twitter will win every lawsuit against spammers or sue every spammer, but it's enough to make a spammer think twice about his future on Twitter – and possibly move to a less litigious or grown-up target.

"We hope the suit acts as a deterrent to other spammers, demonstrating the strength of our commitment to keep them off Twitter," the company's post says.

In a sense, it's a sign of Twitter's further maturation into a real, grown-up company.

Spam was once seen as more of an annoyance than an actual problem for Twitter, and the company did little but rely on its users to report any incidences of Twitter spam. But as the service has swelled to a user base of over 140 million active users, Twitter recognized how serious a problem spam is. To combat it, Twitter developed algorithmic solutions that scan tweets for behavioral cues, able to spot signs that point to spambots. And in January, Twitter acquired security firm Dasient, a company that leads in the prevention of "malvertising."

Beyond this, Twitter says it will continue to fight spam through the development of further technical solutions on its own back-end, as well as growing its own in-house anti-spam team.

It's a big step. And really – it's #abouttime.