As spam volumes continue to decline, spammers are turning their attention to texting, according to a report released Monday by Cloudmark.
A number of factors are attracting spammers to SMS as a delivery vehicle for their digital detritus, not the least of which is trust.
"Phones are a much more trusted device than email, which makes them attractive to spammers," Cloudmark threat researcher Andrew Conway said in an interview.
That trust can be converted into eyeballs for spammers. People open SMS messages at rates exceeding 90%, according to the Cloudmark's 2012 Messaging Threat Report. By contrast, email open rates are in the 20-to-25-percent range.
[See also: Mobile malware shifting to SMS fraud]
Moreover, text messages are typically opened immediately, while the average wait time for an email message is 24 hours.
More and more people are receiving SMS spam messages than ever, according to the report. Some 60% of U.S. adults say they've received spam SMS messages within the last year. Of those receiving the messages, 13% clicked on links in the messages and nine percent called phone numbers in them.
"A text message has a much more powerful psychological impact than an email, which would probably be discarded," said Alex Balan, head of product management for BullGuard, a cyber security company in Romania. "I'm afraid people aren't paranoid enough to ignore spam text messages."
The report also noted that more than a third (41%) responded to a message with the word "stop."
"Stop will work if the text is a genuine marketing email from real company," Conway explained. "If it's a phishing attack or a scam, stop will just alert them that this is a real phone number; they've got a live one here."
Spam messages should be forwarded to 7726, he added. That number sends them to a spam clearinghouse maintained by all the major phone carriers so they can collectively fight the spam campaign at the same time.
SMS spammers grew more sophisticated, and more prolific, in their campaigns during 2012, the report noted.
Cloudmark said it identified 359,000 unique SMS spam pitches in 2012, an average of 30,000 a month. "2013 may be a pivotal year for malware developments in the smartphone arena," the report said.
One sophisticated attack in 2012 involved a piece of Android malware called Spam Soldier. "Before Spam Soldier, Android malware was typically localized," Balan said. "Once you get it, you don't spread it."
Spam Soldier, though, augmented its reach by sending spam messages with infected links to contacts in the address book of the infected phone.
Spam sent from the phone and any replies to those messages were hidden from the operator by the malware. "You won't see anything until you see your phone bill," he said.
Pricing schemes for text messaging have also contributed to the popularity of texting for spammers, said Conway. Because it's a lot easier to get an unlimited texting plan, he explained, a spammer can buy a bunch of SIM cards, put them in a box and start war dialing text messages.
"If you're not paying by the text message, if you're on an unlimited plan, that becomes much more cost effective for the spammer," he said.
Will SMS spam get as bad as email spam in its heyday? "I don't believe it will get as bad as email spam at its worst," Conway said. "I do suspect that it will get worse before it gets better."
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