Rise of SMS Blasters: How Criminals Are By-Passing Phone Scam Detection Systems with Fake Cell Towers
In a new tactic employed by cybercriminals, millions of fraudulent text messages are being sent en masse to unsuspecting recipients. Traditionally, scammers send waves of phishing texts to phones using large databases and automated message-sending systems. However, with increasing efforts from phone companies and telecom services to detect and prevent such scams, criminals have turned to a more covert method: the use of mobile towers replicas, or SMS blasters, placed in vehicles and used to send messages directly to nearby phones.
Over the past year, there has been a significant surge in the utilization of these SMS blaster devices by scammers, with authorities in various countries apprehending individuals using them. The compact devices, often found in the trunks of cars or backpacks, mimic cell phone towers and force phones to connect to insecure networks. Once connected, the devices push scam messages containing links to fraudulent websites to the phones involved.
While the technology behind SMS blasters is not novel, its application in scamming was initially detected in Southeast Asia and has since expanded to Europe and South America. Last week, Switzerland’s National Cybersecurity Centre issued a warning about SMS blasters, highlighting their ability to send large volumes of scam texts indiscriminately. Some blaster devices can even send messages to all phones within a 1,000-meter radius, while reports from an incident in Bangkok suggest that a single blaster was capable of sending approximately 100,000 SMS messages per hour.
Cathal Mc Daid, VP of Technology at telecommunication and cybersecurity firm Enea, has been monitoring the use of SMS blasters. According to Mc Daid, “This marks the first instance in which we have observed large-scale usage of mobile radio-transmitting devices by criminal groups.” While a certain level of technical expertise is required to operate these devices, individuals running them do not necessarily need to be experts—as evidenced by reports of arrests involving individuals paid to drive around areas with SMS blasters in cars or vans.
SMS blasters function as illegitimate phone masts, often referred to as cell-site simulators (CSS). These devices share similarities with so-called IMSI catchers, or “Stingrays,” used by law enforcement for data collection purposes. However, unlike Stingrays, SMS blasters transmit false signals to targeted devices instead of being utilized for surveillance.
Phones within range of a blaster can be compelled to connect to its illegitimate 4G signals before the blaster forces them to downgrade to less secure 2G connections. “The downgraded 2G fake base station is then used to send malicious SMS messages to the mobile phones initially captured by the 4G false base station,” Mc Daid explains. The entire process—capture, downgrade, and message transmission—can occur in under 10 seconds, often going unnoticed by recipients.
The rise of SMS blasters coincides with an uptick in scam activities. As technology companies and mobile network operators have strengthened their protections against fraudulent text messages over the years, this new method of delivery presents a significant challenge for those aiming to prevent such scams. Despite efforts to bolster security measures, millions of scam messages continue to bypass detection systems.
