About 750 Twitter accounts were hacked last week and used to send tweet spam.

"Today we discovered about 750 Twitter accounts were broken into and had a link to a Webcam site posted on the accounts," the company said on its blog on Friday. "It appears other sites and services have been affected by a similar attack. We reset the passwords of the compromised accounts and removed the spammy updates. Our safety team is currently investigating the attack."

The spam links were attempting to drive traffic to a porn Webcam site. Graham Cluley, security researcher at Sophos, observes that Facebook users last month were hit with a similar attack promoting the same porn Web site.

Twitter did not respond to a request for further information about the attack. But based on the company's advice about using strong passwords, it may be that the hacker(s) guessed the victims' passwords, possibly through what's known as a dictionary attack.

A dictionary attack, as its name suggests, involves randomly trying every word in a dictionary file as a possible password. It's for this reason that users are advised never to use single words in any language as a password.

Twitter was hacked in January using a dictionary attack. According to Wired News, an 18-year-old hacker calling himself GMZ gained access to the account of a Twitter employee that month using a dictionary-attack program that he created.

He said he then offered members of an online forum access to Twitter accounts upon request, which led to the hijacking of Twitter accounts associated with Facebook, Fox News, The Huffington Post, Barack Obama, Britney Spears, and CNN's Rick Sanchez.

The incident last week adds to a growing list of Twitter security failures. Beyond this one and the similar one in January, spammers in December created a Twitter account in the name of Google Internet evangelist Vint Cerf and used it for spamming. In July, security researcher Aviv Raff said that Twitter suffered from a vulnerability that allowed an attacker to force victims to join his or her Twitter follow list automatically.

In January, Twitter said, "We are engaged in a full security review of all access points to Twitter." The company has not yet disclosed the results of its review.

InformationWeek Analytics has published an independent analysis of the challenges around setting business priorities for next-gen Web applications, including security. Download the report here (registration required).