The major mobile networks account for 90 percent of all legitimate text message traffic -- but only 38 percent of blocked spam messages. The rest of the spam messages is dominated by network unaffiliated virtual operators, according to a new report from Cloudmark.
These companies, known as NUVOs, provide app-based text messages for mobile phone users. But instead of sending messages to other users of the same app -- like, say, Facebook, Skype, or WhatsApp -- the NUVOs transmit the messages over traditional networks, so that anyone with a cell phone number can get the messages and respond to them.
Popular examples include HeyWire, Pinger’s TextFree, Gogii’s TextPlus, Google Inc.’s Voice, Toktumi Line 2, Twilio, and Hook Mobile.
"Communication is possible between any two parties with a phone number," said Tom Landesman, security researcher at San Francisco-based Cloudmark, Inc.. "And no special app is required by the receiver."
The industry trade group Cellular Telephone Industries Association, which is composed of the mobile network operators as well as some of the virtual operators, is very active in fighting abuse, according to Cloudmark -- but many NUVOs aren't members.
Text messages sent through NUVOs start out inside the apps, but then go through the usual big-name mobile network operators, who have processes in place to spot problems.
However, since the NUVOs lease services from multiple providers, and the messages come from virtual accounts and not actual mobile phone numbers, it's harder for the mobile phone companies to stop the spammers.
In addition, NUVOs offer application interfaces that can make some forms of abuse more accessible, said Landesman.
As a result, NUVOs, which are the source of just 9 percent of legitimate text messages, account for 37 percent of the spam.
The other 25 percent of spam messages come from uncategorized sources, according to Landesman -- sources which include thousands of smaller services that all together account for less than 2 percent of the legitimate traffic.
"Likely these are more NUVOs," he added. "However, I can’t say that with certainty since they fell outside the scope of this analysis."
Cloudmark provides spam filters for many of the U.S. mobile operators, and see this traffic first-hand.
The spam texts clogs up networks and drives up mobile phone bills, but also serve as a security threat, especially for companies that allow employees to use personal devices for work.
"There have been a number of exploit chains that start from SMS messages and lead to a myriad of compromises," said Landesman.
People tend to trust their mobile devices and use them to store sensitive information, he added, and attackers can use text messages to abuse that trust.
It's one of the reasons why text messages have been deprecated as an out-of-band form of second factor authentication in the latest NIST draft, he said.
Cloudmark also reported that two small countries, Vietnam and Bangladesh, were starting to make a big splash when it comes to spam.
Email sent from Vietnam and Bangladesh to mailboxes protected by Cloudmark were 66 percent and 59 percent spam, respectively, according to the company's report. The U.S. and other wealthier nations were top targets.