AOL has issued a warning to users that their personal information has been stolen by attackers, a week after the security of its servers was questioned.

The net giant on Monday said that the same hackers behind last week's spam deluge were able to infiltrate its servers and lift information including email addresses, contact lists and home mailing addresses. Additionally, encrypted passwords and security question-answer pairs were stolen.

AOL kicked off an investigation last week when users began receiving large amounts of spam from spoofed email addresses. The company believes the flood, which circumvented most spam controls, was the result of a security breach that the company estimates encompassed about two per cent of AOL's customer email accounts.

"Importantly, we have no indication that the encryption on the passwords or the answers to security questions was broken," AOL said.

"In addition, at this point in the investigation, there is no indication that this incident resulted in disclosure of users' financial information, including debit and credit cards, which is also fully encrypted."

The company is working with law enforcement to track down the individuals behind the breach.

In the meantime, AOL is advising users to be wary of suspicious email messages, and to refuse to hand over personal information or account details to anyone claiming to be an AOL administrator. Additionally, users are advised to change their passwords.

"Although there is no indication that the encryption on the passwords or answers to security questions was broken, as a precautionary measure, we nevertheless strongly encourage our users and employees to reset their passwords used for any AOL service and, when doing so, also to change their security question and answer," AOL said.

The recommended steps are all best practices which should be observed by all users regardless of service provider. Though given that the AOL email service traces its roots back two decades to the era of dial-up walled garden ISPs, the company might face an uphill battle in educating users who might be... how do we put this?... unfamiliar with modern security practices. ®