A fix against an SMS spoofing flaw involving micro-blogging service Twitter offers only partial protection.
Tests by Heise Security found that providing a user knew the number of a phone associated with a Twitter account, it would be possible to use an SMS sender faking service to post fake status updates that appeared under a user's profile. Services such as PhonyText allow the relaying of SMS messages with a fake sender field. Spoofed SMS messages sent through this service to the number for sending SMS tweets could thus be used to create fake tweets.
In this way, providing you knew the mobile number associated with accounts, it might be possible to suggest that Stephen Fry was once again stuck in a lift instead of whale-watching off the coast of Mexico or that Britney's vagina had grown claws as well as teeth. It might be even possible to claim something even more ridiculous, for example that Arsene Wenger had agreed to manage Manchester City next season.
Many Twitter instructions beyond simple status updates are possible via text message. This makes it potentially possible to alter account settings via text, creating a possible means to sign people onto premium rate text services, the Washington Post's Security Fix blog reports.
According to Security Fix, Twitter fixed the authentication flaw on Wednesday. However, Heise Security's tests show that the fix is, as yet, incomplete.
US-based mobile carriers have deployed measures in place to prevent SMS spoofing so that the issue involves Twitter gateways outside the US. Faked messages involving US numbers sent through these gateways may still pose a problem. Twitter users are advised to use the SMS PIN option to tamper-proof their text message tweets.
Security researcher Lance James identified the latest vulnerability involving Twitter and SMS spoofing, but the attack vector is not new. Security researcher Nitesh Dhanjani pinpointed a very similar threat to Twitter involving SMS spoofing in April 2007, at which point Twitter introduced PIN protection. ®