Security company Insert has issued a warning about a serious flaw in Google’s Gmail, which can turn the free email service into an effective spamming tool.

Insert has worked out a way that a hacker could take advantage of the trust that exists between mail service providers and the way that Google forwards messages.

According to the company spammer could use Google’s SMTP service to send thousands of bulk e-mails.
This would ignore Google's 500-address e-mail limit and any identity fraud protection.

The attack is based on the concept that e-mail providers are using white and blacklists to root out spammers. Since most white lists name Gmail, any messages are given free access to addresses and ignore spam filtering.

The hacker does not need any special internet access privileges other than being able to connect to SMTP (TCP port 25) and HTTP (TCP port 80) servers.

So far Google has not commented on the flaw. X