The biggest trends of the quarter are viruses being sent in attachments and the resurgence of image spam, Google said in a blog post Wednesday. And, despite taking a dip during the quarter, spam levels are still up compared to the previous quarter, Adam Swidler, senior product marketing manager at Google, told SCMagazineUS.com on Thursday.
In early June, the amount of unwanted mail decreased by 30 percent overall when rogue internet service provider 3FN, which also did business as Pricewert and Telecom, was taken down by the Federal Trade Commission, Swidler said. Since then, spam volume is not yet back up to pre-3FN takedown levels – it's about halfway there, having increased by 14 percent since the initial drop.
In contrast, security vendors, Marshal8e6 and Symantec previously noted that the 3FN takedown only had a minor impact on spam volume. Less than a week after the 3FN takedown, Marshal8e6 said spam levels were back up to levels they were before.
Swidler said he cannot comment on other companies' findings, but Google's spam data comes from processing 3.5 billion emails a day, giving them a very comprehensive view of spam trends, he said.
One interesting spam trend to note is that volumes have recently been subject to a more drastic “ebb and flow,” Swidler said. Previously, there was always a pretty stable and predictable increase in spam from month to month. But recently, the McColo and 3FN takedowns have caused spam volume to see more dramatic peaks and valleys.
Another notable spam trend during Q2, also related to the 3FN takedown, is an increase of spam that contains malicious attachments, Swidler said. During Q2, the volume of this type of spam was the highest it has been in two years. This can likely be attributed to spammers aiming to rebuild their networks of infected computers.
Spammers are also frequently employing an older trend of sending spam that includes images, Swidler said. “Image spam” has been common with spammers since 2007, but recently saw a new surge of popularity. Image spam "can also include malicious links or content – and either way, the large file size of an image spam can place a heavy load on an email network,” Google said.
A possible explanation for the rise is attackers testing spam filters to determine which tactics are effective, Swidler said, although many anti-spam filters today will catch this type of spam content.