Cybercriminals have a new way of sending millions of scam text messages to people. Typically when fraudsters send waves of phishing messages to phones—such as toll or delivery scams—they may use a huge list of phone numbers and automate the sending of messages. But as phone companies and telecom services have rolled out more tools to detect scams in texts, criminals have started driving around cities with fake cell phone towers that send messages directly to nearby phones.
Over the last year, there has been a marked uptick in the use of so-called “SMS blasters” by scammers, with cops in multiple countries detecting and arresting people using the equipment. SMS blasters are small devices, which have been found in the back of criminals’ cars and sometimes backpacks, that impersonate cell phone towers and force phones into using insecure connections. They then push the scam messages, which contain links to fraudulent websites, to the connected phones.
While not a new type of technology, the use of SMS blasters in scamming was originally detected in Southeast Asian countries and has increasingly spread to Europe and South America—just last week, Switzerland’s National Cybersecurity Centre issued a warning about SMS blasters. The devices are capable of sending huge volumes of scam texts indiscriminately. The Swiss agency said some blasters are able to send messages to all phones in a radius of 1,000 meters, while reports about an incident in Bangkok say a blaster was used to send around 100,000 SMS messages per hour.
“This is essentially the first time that we have seen large-scale use of mobile radio-transmitting devices by criminal groups,” says Cathal Mc Daid, VP of technology at telecommunication and cybersecurity firm Enea, who has been tracking the use of SMS blasters. “While some technical expertise would help in using these devices, those actually running the devices don’t need to be experts. This has been shown by reports of arrests of people who have been basically paid to drive around areas with SMS blasters in cars or vans.”
SMS blasters act as illegitimate phone masts, often known as cell-site simulators (CSS). The blasters are not dissimilar to so-called IMSI catchers, or “Stingrays,” which law enforcement officials have used to scoop up people’s phone data. But instead of being used for surveillance, they broadcast false signals to targeted devices.
Phones near a blaster can be forced to connect to its illegitimate 4G signals, before the blaster pushes devices to downgrade to the less secure 2G signal. “The 2G fake base station is then used to send (blast) malicious SMSes to the mobile phones initially captured by the 4G false base station,” Mc Daid says. “The whole process—4G capture, downgrade to 2G, sending of SMS and release—can take less than 10 seconds,” Mc Daid explains. It’s something people who receive the messages may not even notice.
The growth of SMS blasters comes at a time when scams are rampant. In recent years, technology firms and mobile network operators have increasingly rolled out greater protections against fraudulent text messages—from better filtering and detection of possible scam messages to blocking tens of millions of messages per month. This month, UK telecom Virgin Media O2 said it has blocked more than 600 million scam text messages during 2025, which is more than its combined totals for the last two years. Still, millions of scam messages get through, and cybercriminals are quick to try to evade detection systems.