The amount of spam hitting company networks in the past several months has exploded and those fighting the spam battle say it's also smuttier than ever.

Today, email inboxes are being flooded with about 400% more unsolicited bulk email, or spam, than they were back in September, according to new numbers published by Brightmail Inc., a San Francisco-based anti-spam company that sells software and rules to filter out spam.

And brand new numbers from one of the largest anti-spam organizations, Mail-Abuse Prevention Systems LLC (MAPS), shows that 600% to 700% more spam was sent out between April and June of this year compared to the same time frame last year.

"It's definitely higher than I thought it would be. It's kind of terrifying," says Margie Arbon, director of operations at MAPS. "This is a huge drain on companies trying to deal with it. Most companies are paying for bandwidth. They're having to pay to have this stuff delivered. They're having to buy bigger harddrives, bigger hardware, extra servers and the manpower to handle it...Companies are struggling with this even more now."

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Ken Schneider, chief technology officer at Brightmail, says spam has long plagued large ISPs, but this recent deluge means that it's weighing heavily on smaller ISPs and corporations.

"There's been explosive growth over the last nine months," says Schneider. "The percentage of email that is spam has gone from 10% to 20%. If you get five messages in corporate mail, one of those is going to be spam. If you're a large ISP, half your mail could easily be spam."

Graphic Subject Lines, Graphic Images

And Schneider says there isn't simply more spam these days. There's a lot more pornographic spam, with far more graphic subject lines and a higher percentage that come with graphic images.

"Spam is a nuisance to a lot of people," says Schneider. "But when it's pornographic, it causes a lot more pain to a company or an ISP because it's so much more bothersome for employees. It's so much more in-your-face lately. The subject lines are smuttier."

The subject lines are often misleading, even using the recipient's name to fool people into opening the email to find pornographic messages and photos.

Arbon says at MAPS they don't track the content of the spam but they are noticing that an increasing number of "legitimate" companies are sending out spam as part of their marketing strategies.

"I've seen a huge increase in very legitimate companies making some interesting choices in who they're using to send out mail," says Arbon. "A lot of places that claim to have totally opt-in lists don't...I don't think they understand what it is they're doing. I think a backlash is coming and a lot of these companies are naively thinking this is OK because that's what their marketing people are telling them."

This influx of spam is driving a lot of companies to take extreme measures to keep their networks from buckling under the weight of it all, according to Arbon. Some companies, she says, are using multiple blackhole lists, they're making their own lists and they're even blocking out email from entire countries or regions, such as Asia.

And Arbon notes that many spammers have moved their operations overseas so a great percentage of spam is coming from Eastern European countries, South America and Asian countries. "Spammers are using countries that are just a little behind the technology curve," says Arbon. "They may not be aware of the issues involved, or they're not set up to respond to the issues or perhaps there are economic conditions that make the cash flow more appealing than dealing with the consequences."

But Arbon and Schneider both agree that blocking out entire countries or regions is not a good tactic to take, because it cuts a company off from receiving legitimate email that could be coming from or through that region. And Arbon points out that a high percentage of spam is still coming from the United States.

"There was always the concern that people would be missing legitimate email but I see that fading rapidly," says Arbon. "The economy isn't great. Companies don't have the staff to deal with it. ISPs can't afford to man their abuse complaint desks like they should. It's a vicious cycle."