Twitter was hit by two different rounds of phishing Thursday, as criminals tried to take control of user accounts and then use them as a springboard to attack others.

Both Twitter and Facebook have been hit with phishing attacks in recent days. "The social networking attacks are becoming increasingly common," said Jamie De Guerre, chief technology officer with antispam vendor Cloudmark. "Spammers are really moving to attack social networks because of the popularity of the social networks and also because they're not as well defended as most e-mail platforms."

Twitter was hit by another in January. This latest attack had snagged several hundred victims by mid-day Thursday.

Here's how Thursday's attack worked: In the first Twitter phishing round, hackers created fake Twitter accounts and then started following legitimate Twitter users. Twitter notifies users when they have new followers, sending the user a link to the follower's Twitter profile page. In this case, the profile page contained a link to a phishing site. So the victim, while investigating his new follower, would end up on the fake site Tvviter(.)com (this page is not safe to visit) where he would be asked to enter his Twitter username and password.

Once the phishers obtained their victim's login credentials, they used them to launch the second round of attacks. In this round, they posted Twitter messages such as "hey check thiss out" or "Hey. there is this funny blog going around." These messages include