Although these spear-phishing attacks didn't affect a lot of users, attacks on Web-based e-mail accounts have become a common problem for companies such as Google, Microsoft and Yahoo. Just last month Microsoft patched a Web . Security vendor Trend Micro said that that flaw was used to steal e-mail messages.

Webmail accounts are often hit with less sophisticated, widespread attacks, too. Scammers like hacked e-mail accounts because they can use them to circumvent spam filters. Even users who do not handle sensitive information routinely find their Webmail accounts broken into and used to promote things such as illegal pharmaceutical websites.

Google has notified the victims of the attack and secured their accounts. The company has also "notified relevant government authorities," it said in its blog post.

The IDG News Service