A security researcher today provided a way for users to see whether their e-mail addresses and passwords were among the 1.3 million compromised in a hack of Gawker Media's sites.

HD Moore, chief security officer at Rapid7 and the creator of the open source Metasploit penetration-testing toolkit, came up with a down-and-dirty way for users to search the list of purloined account information without having to download the massive 487MB file from the Internet.

On Sunday, Gawker, which operates several popular technology sites, including Gizmodo and Lifehacker, confirmed that its servers had been hacked, and that hundreds of thousands of registered users' email addresses and passwords had been accessed. A group calling itself "Gnosis" claimed credit for the attack, and said it had obtained more than 1.3 million accounts.

Gawker apologised for the breach, and urged users to change their passwords. If that password was used for accessing other sites, Gawker recommended that users change it for those destinations as well.

"It's best to assume that your username and password were included among the leaked data," Gawker said in an FAQ it posted on the Lifehacker site.

Moore had a better idea, and has assembled a way for people to check whether their account, including their password, has been compromised.

In an email to Computerworld Monday, Moore spelled out the technique:

Step 1: Go to http://pajhome.org.uk/crypt/md5/, enter an email address in the 'Input' field, click the 'MD5' button, then copy the hash from the 'Result' field.

Step 2: Go to http://www.google.com/fusiontables/DataSource?dsrcid=350662, click 'Show Options,' then paste the already-obtained hash in the field to the right of the '=' symbol. Change the left-most field to 'MD5.' Click 'Apply.'

If the email address is among those compromised, the search will show a result.

Although Gawker said it encrypted users' passwords, some passwords have already been decrypted by Gnosis.

Moore used MD5 hashes of the email addresses in the list he posted as a Google Fusion Table so users could check whether their accounts had been compromised without exposing the addresses a second time.

"This is a little clunky, but [it] works," he said.