Vulnerabilidade em modems DSL afecta 4,5 milhões no Brasil

DSL modem hack used to infect millions with banking fraud malware
ArsTechnica

Millions of Internet users in Brazil have fallen victim to a sustained attack that exploited vulnerabilities in DSL modems, forcing people visiting sites such as Google or Facebook to reach imposter sites that installed malicious software and stole online banking credentials, a security researcher said.

The attack, described late last week during a presentation at the Virus Bulletin conference in Dallas, infected more than 4.5 million DSL modems, said Kaspersky Lab Expert Fabio Assolini, citing statistics provided by Brazil's Computer Emergency Response Team. The CSRF (cross-site request forgery) vulnerability allowed attackers to use a simple script to steal passwords required to remotely log in to and control the devices. The attackers then configured the modems to use malicious domain name system servers that caused users trying to visit popular websites to instead connect to booby-trapped imposter sites.

"This is the description of an attack happening in Brazil since 2011 using 1 firmware vulnerability, 2 malicious scripts and 40 malicious DNS servers, which affected 6 hardware manufacturers, resulting in millions of Brazilian internet users falling victim to a sustained and silent mass attack on DSL modems," Assolini wrote in a blog post published on Monday morning. "This enabled the attack to reach network devices belonging to millions of individual and business users, spreading malware and engineering malicious redirects over the course of several months."

Assolini said the mass attack was the result of a "perfect storm" brought on by the inaction of a variety of key players, including ISPs, modem manufacturers, and the Brazilian governmental agency that approves network devices, but failed to test any of the modems for security.

It remains unclear which modem manufacturers and models are susceptible to the attacks. Assolini said a vulnerability disclosed in early 2011 appears to be caused by a chipset driver included with modems that use hardware from communications chip provider Broadcom. It allows a CSRF attack to take control of the administration panel and capture the password set on vulnerable devices. Assolini doesn't know precisely when, but at some point attackers began exploiting the vulnerability on millions of Brazilian modems. In addition to pointing the devices to malicious DNS servers, the attackers also changed the device passwords so it would be harder for victims to change the malicious settings.


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