If you've been noticing more spam in your Gmail of late, you are not the only one. A new report by Google today shows that spam is on the rise.

Why? It's still a profitable business.

Google filters around 3 billion to 3.5 billion spam messages a day for its upwards of 50,000 customers.

But spam volumes were up 53% in the second quarter of the year, according to Adam Swidler, product marketing manager for Google Enterprise.

Last month, the Federal Trade Commission got a restraining order to shut down Pricewert, an ISP that did business under the names 3FN and APS Telecom, and spam rates fell 30%. But in just a month later, spam rates have risen again.

But spam technology isn't change as much as its frequency. Google's Amanda Kleha thinks that this could be attributed to new spammers filling the void left by 3FN and APS by flooding inboxes with trusty but flawed spam techniques. That means image spam is back. But the largest spam attacks in the last quarter were based on an old school "newsletter" templates (which include malicious link attachments). 

What these tricks lack in sophistication they make up for in volume. The worst attack was on June 18, when Google "tracked a new attack that unleashed 50% of a typical day's spam volume in just two hours' time."

According to Swidler: "The bottom line is there's money to be made by the activities that these folks do."

MessageLabs Intelligence released numbers this week that place email spam levels at a staggering 90.4% of all email traffic in June, which makes you really appreciate your spam filter. And the profit margin becomes even more enticing for spammers when they don't need to use humans to do their dirty work (80% of all spam sent today comes from botnets)

From The Google Enterprise Blog:

"In summary, Q2'09 saw continued unpredictability and the resurgence of old-style spam attacks. Are spammers finally running out of original ideas? And if so, like Hollywood, are we now starting to see spam 'remakes,' based on originals of a few years ago? And what are spammers looking to accomplish as they unleash these remakes? Only time will tell."

Based in New York, Meghan Keane is US Editor of Econsultancy. You can follow her on Twitter: @keanesian.