Tag Archive: Abbotsford Computers

Critical crypto bug leaves Linux, hundreds of apps open to eavesdropping

Hundreds of open source packages, including the Red Hat, Ubuntu, and Debian distributions of Linux, are susceptible to attacks that circumvent the most widely used technology to prevent eavesdropping on the Internet, thanks to an extremely critical vulnerability in a widely used cryptographic code library.

The bug in the GnuTLS library makes it trivial for attackers to bypass secure sockets layer (SSL) and Transport Layer Security (TLS) protections available on websites that depend on the open source package. Initial estimates included in Internet discussions such as this one indicate that more than 200 different operating systems or applications rely on GnuTLS to implement crucial SSL and TLS operations, but it wouldn’t be surprising if the actual number is much higher. Web applications, e-mail programs, and other code that use the library are vulnerable to exploits that allow attackers monitoring connections to silently decode encrypted traffic passing between end users and servers.

The bug is the result of commands in a section of the GnuTLS code that verify the authenticity of TLS certificates, which are often known simply as X509 certificates. The coding error, which may have been present in the code since 2005, causes critical verification checks to be terminated, drawing ironic parallels to the extremely critical “goto fail” flaw that for months put users of Apple’s iOS and OS X operating systems at risk of surreptitious eavesdropping attacks. Apple developers have since patched the bug.

“It was discovered that GnuTLS did not correctly handle certain errors that could occur during the verification of an X.509 certificate, causing it to incorrectly report a successful verification,” an advisory issued by Red Hat warned. “An attacker could use this flaw to create a specially crafted certificate that could be accepted by GnuTLS as valid for a site chosen by the attacker.”

GnuTLS developers published this bare-bones advisory that urges all users to upgrade to version 3.2.12. The flaw, formally indexed as CVE-2014-0092, is described by a GnuTLS developer as “an important (and at the same time embarrassing) bug discovered during an audit for Red Hat.” Debian’s advisory is here.

As was the case with last week’s critical encryption bug from Apple, the GnuTLS vulnerability is the result of someone making mistakes in source code that controls critical functions of the program. This time, instead of a single misplaced “goto fail” command, the mistakes involve errors with several “goto cleanup” calls. The GnuTLS program, in turn, prematurely terminates code sections that are supposed to establish secure TLS connections only after the other side presents a valid X509 certificate signed by a trusted source. Attackers can exploit the error by presenting vulnerable systems with a fraudulent certificate that is never rejected, despite its failure to pass routine security checks. The failure may allow attackers using a self-signed certificate to pose as the cryptographically authenticated operator of a vulnerable website and to decrypt protected communications. It’s significant that no one managed to notice such glaring errors, particularly since they were contained in code that anyone can review.

Security researchers are still studying the vulnerability and assessing its effect on the wide array of OSes and applications that depend on GnuTLS. For the moment, readers should assume that the severity is critical given the dizzying amount of downstream code that may be affected. One example: the apt-get installer some distributions of Linux use to distribute and update applications relies on GnuTLS, although exploits against the package can probably be caught by cryptographic code-signing of the downloaded program (thanks to readers for pointing out this secondary level of protection). Version 3 of lib-curl, which is distributed in Debian and Ubuntu, also depends on GnuTLS. Some Debian- and Ubuntu-based virtual private networking applications that work with Cisco Systems hardware are also affected. This list goes on and on.

Source: ArsTechnica

Sophisticated botnet steals more than $47M by infecting PCs and phones

A new version of the Zeus trojan—a longtime favorite of criminals conducting online financial fraud—has been used in attacks on over 30,000 electronic banking customers in Europe, infecting both their personal computers and smartphones. The sophisticated attack is designed to circumvent banks’ use of two-factor authentication for transactions by intercepting messages sent by the bank to victims’ mobile phones.

The malware and botnet system, dubbed “Eurograbber” by security researchers from Check Point Software and Versafe, was first detected in Italy earlier this year. It has since spread throughout Europe. Eurograbber is responsible for more than $47 million in fraudulent transfers from victims’ bank accounts, stealing amounts from individual victims that range from 500 Euros (about $650) to 25,000 Euros (about $32,000), according to a report published Wednesday.

The malware attack begins when a victim clicks on a malicious link, possibly sent as part of a phishing attack. Clicking on the link directs them to a site that attempts to download one or more trojans: customized versions of Zeus and its SpyEye and CarBerp variants that allow attackers to record Web visits and then inject HTML and JavaScript into the victim’s browser. The next time the victim visits their bank website, the trojans capture their credentials and launch a JavaScript that spoofs a request for a “security upgrade” from the site, offering to protect their mobile device from attack. The JavaScript captures their phone number and their mobile operating system information—which are used in the second level of Eurograbber’s attack.

With the phone number and platform information, the attacker sends a text message to the victim’s phone with a link to a site that downloads what it says is “encryption software” for the device. But it is, in fact, “Zeus in the mobile” (ZITMO) malware—a Trojan crafted for the Android and BlackBerry mobile operating systems that injects itself between the user and the mobile browser and SMS messaging software. With both devices now compromised, the malware waits for the victim to access a bank account, and then immediately transfers a percentage of the victim’s balance to an account set up by the criminals running the botnet.

The malware then intercepts the confirmation text message sent by the bank, forwarding it to the trojan’s command and control server via a relay phone number. The server uses the message to confirm the transaction and withdraw the money. The same process happens every time the victim logs into their bank account, gradually withdrawing money without alerting the user.

Both Checkpoint and Versafe have added signature and behavior detection to their malware protection products that can block Eurograbber. Updating software that is a frequent target for Web “driveby download” exploits—such as Adobe Flash, Java, and Web browsers—can help prevent infection by the malware, as can a healthy amount of paranoia about clicking links in e-mails.

Source: Arstechnica