Twitter was not affected by the Heartbleed Internet vulnerability that rocked the Web security world this week, making one less password consumers need to change to protect themselves, but users still need to be careful how they respond to the threat.
Heartbleed is a bug in OpenSSL (Secure Sockets Layer), a tool for securing Web connections, that could let attackers steal data from server memory 64KB at a time. It could be automatically run multiple times without leaving any evidence, potentially collecting user names and passwords as well as encryption keys and certificates for decrypting private data, researchers say.
Twitter declared itself in the clear on Tuesday afternoon, posting a brief statement on its Status page.
"On 4/7/2014 we were made aware of a critical vulnerability in OpenSSL (CVE-2014-0160), the security library that is widely used across the internet and at Twitter," the company wrote. "We were able to determine that twitter.com and api.twitter.com servers were not affected by this vulnerability. We are continuing to monitor the situation."
Some other big Web names, including Yahoo, Facebook, Google and Microsoft, said they either are studying the problem or have fixed it on their sites. If they were vulnerable, they were not alone: Internet security company Netcraft estimates that about 500,000 sites had the bug. Late Wednesday, there did not appear to be any reports of exploits against the flaw.
Another piece of good news: No version of Android was affected, with the limited exception of Android 4.1.1, according to Google.
If Twitter's servers weren't affected by Heartbleed, its subscribers don't need to take the extra few minutes to change their Twitter passwords as they go through updating their other accounts in the wake of the disclosure, said Lamar Bailey, director of security research for security vendor Tripwire. Twitter might have dodged the bullet by running a different version of SSL or by turning off the vulnerable feature in OpenSSL, he said.
Heartbleed is an apparently accidental bug introduced through an update to OpenSSL at the end of 2011. It opened the door for attackers to misuse a "heartbeat" feature that's commonly used to tell whether a user's session on a site is still active, Bailey said.
The tricky thing about Heartbleed is that it was out in the field from that release until a recent update that fixed the problem. Hackers could have exploited the hole at any time during that period and stolen data without leaving a trace. So users should look for Web companies to take two steps to make their sites secure, Bailey said.
The first is to replace the site's SSL mechanism, either by applying a new version or recompiling their current version with the vulnerable feature turned off. The second is to replace the private keys and certificates used to decrypt the data on its servers, because if they've been compromised, even new passwords won't protect users, he said.
Even patching SSL is no simple task, Bailey said. Sites may be running multiple versions of SSL, so administrators have to take care to be thorough and keep testing for the vulnerability, he said. Small businesses, in particular, may not get their sites fixed for some time, Bailey said.
On Wednesday, Yahoo acknowledged its platform was vulnerable to Heartbleed and said it started working on a fix as soon as it knew about the problem.
"Our team has successfully made the appropriate corrections across the main Yahoo properties (Yahoo Homepage, Yahoo Search, Yahoo Mail, Yahoo Finance, Yahoo Sports, Yahoo Food, Yahoo Tech, Flickr and Tumblr) and we are working to implement the fix across the rest of our sites right now," a company representative said via email.
Google has also been working on the problem. "We've assessed this vulnerability and applied patches to key Google services such as Search, Gmail, YouTube, Wallet, Play, Apps, and App Engine. Google Chrome and Chrome OS are not affected. We are still working to patch some other Google services," the company said in a blog post. Among those were Cloud SQL and Google Search Appliance. For customers of Google Compute Engine, the company laid out steps that users themselves need to take.
Facebook said it had added protections to its OpenSSL implementation before the problem was publicly disclosed and was still watching the situation. "We haven't detected any signs of suspicious account activity that would suggest a specific action, but we encourage people to take this opportunity to follow good practices and set up a unique password for your Facebook account that you don't use on other sites," Facebook said in a statement.
"We are following reports of an OpenSSL library issue. If we determine there is an impact to our devices and services, we'll take necessary steps to protect our customers," a Microsoft representative said.