Topic: Email-stealing worm slithers across LiveJournal (Samy Worm, allowScriptAccess)

[Samker]

LiveJournal's security team has disabled some media features on the blogging site after a quick-spreading worm stole user email addresses and caused entries designated as private to be available to everyone.

The self-propagating exploit spread to users who were logged in and did nothing more than view a LiveJournal posting that was already infected. Affected account holders had their email addresses stolen and found that their privacy settings were lowered so that posts that may have been restricted were generally available. The worm then embedded code into infected accounts that attacked other LiveJournal users.

"What occurred today caused a limited but serious privacy breach, so we are making this post in order to inform you of the issue, what actions this exploit performed, and how to know if you have been affected," LiveJournal staff members wrote in a posting that was commendable for the level of transparency and detail it provided: http://news.livejournal.com/117957.html

Passwords, authentication cookies, and other sensitive data were not intercepted. End users' computers were also left unharmed.

The worm spread through malicious Adobe Flash media files that used "cross-domain scripting" to make the unauthorized account changes. The attack, which lasted for about two hours, was halted on Tuesday at about 8:50 pm California time by disabling the embedding of all video and audio. Since then, staffers have re-enabled content from YouTube and ReTube and plan to expand the list in the coming days.

"It does sound like a worm, and it probably could have been a lot worse," said Mike Bailey, a web application security expert who is a senior researcher at Foreground Security. "I'm fairly impressed that it was found and stopped as quickly as it was."

He added that based on this description of the exploit code, it appeared it was allowed to run wild because a parameter known as "allowScriptAccess" was set on the LiveJournal website: http://community.livejournal.com/meta_lj/567.html
It appeared the setting allowed the malicious Flash file to execute javascript with the privileges of the LiveJournal page, something that should never happen on sites that accept user content.

The exploit harkens back to the so-called Samy Worm, which in 2005 knocked MySpace out of commission after it added a million users to the creator's friends page.

Given the ability of the LiveJournal worm to quickly spread and surreptitiously steal email addresses, it's surprising its authors didn't direct it to do more.

"Which begs the question, was this PoC [proof of concept] or actively malicious?" Jeremiah Grossman, CTO of WhiteHat Security observed. "Or somewhere in between."

The LiveJournal posting speculated that fewer than 100 entries were found to embed the malicious Flash file, but it cautioned the number of infected users was probably higher. Based on the number of users who responded that they were hit by the attack, that appeared to be the case.

The staff has created an easy way for users to check to see if their accounts have been infected. Recent entries of affected accounts will show four boxes at the bottom.

(Register)