Feeds

New trojan in mass DNS hijack

Single box pollutes entire LAN

Beginner's guide to SSL certificates

Researchers have identified a new trojan that can tamper with a wide array of devices on a local network, an exploit that sends them to impostor websites even if they are hardened machines that are fully patched or run non-Windows operating systems.

The malware is a new variant of the DNSChanger, a trojan that has long been known to change the domain name system settings of PCs and Macs alike. According to researchers with anti-virus provider McAfee's Avert Labs, the update allows a single infected machine to pollute the DNS settings of potentially hundreds of other devices running on the same local area network by undermining its dynamic host configuration protocol, or DHCP, which dynamically allocates IP addresses.

"Systems that are not infected with the malware can still have the payload of communicating with the rogue DNS servers delivered to them," McAfee's Craig Schmugar writes here of the new variant. "This is achieved without exploiting any security vulnerability."

The scenario plays out something like this:

  • Jill connects a PC infected by the new DNSChanger variant to a coffee shop's WiFi hotspot or her employer's local network.
  • Steve connects to the same network using a fully-patched Linux box, which requests an IP address.
  • Jill's PC injects a DHCP offer command to instruct Steve's computer to rout all DNS requests through a booby-trapped DNS server.
  • Steve's Linux box can no longer be trusted to visit authoritative websites. Although the address bar on his browser may show he is accessing bankofamerica.com, he may in fact be at an impostor website.

The only way a user might know the attack is underway is by manually checking the DNS server his computer is using (e.g. by typing "ipconfig /all" at a Windows command prompt). There are several countermeasures users can take, Schmugar said, the easiest being hard-coding a DNS server in a machine's configuration settings.

(In Windows, this can be done by going to Start > Control Panel > Network Connections and right clicking on Local Area Connection and choosing properties. Scroll down to Internet Protocol (TCP/IP) and click the Properties button. Then type in the primary and secondary for your DNS service. We're partial to OpenDNS, whose settings are 208.67.222.222 and 208.67.220.220.)

In an interview, Schmugar said the DHCP attack doesn't exploit a vulnerability in either user machines or network hardware, allowing it to work with a wide variety of home and enterprise routers. It involves a ndisprot.sys driver that is installed on the infected box. Once there, it monitors network traffic for DHCP requests and responds with bogus offers that contain the IP address to the rogue DNS server.

DNSChanger has already been viewed exploiting router weaknesses to change DNS settings, but the ability to poison other machine's DHCP connections appears to be new, said Eric Sites, VP of research at Sunbelt Software. For the moment, the new variant doesn't appear to be widely circulated, but the prospect of a trojan that can poison other machines' DHCP connections suggests this one is worth watching. ®

Choosing a cloud hosting partner with confidence

More from The Register

next story
SMASH the Bash bug! Apple and Red Hat scramble for patch batches
'Applying multiple security updates is extremely difficult'
Apple's new iPhone 6 vulnerable to last year's TouchID fingerprint hack
But unsophisticated thieves need not attempt this trick
Oracle SHELLSHOCKER - data titan lists unpatchables
Database kingpin lists 32 products that can't be patched (yet) as GNU fixes second vuln
Who.is does the Harlem Shake
Blame it on LOLing XSS terroristas
Researchers tell black hats: 'YOU'RE SOOO PREDICTABLE'
Want to register that domain? We're way ahead of you.
Stunned by Shellshock Bash bug? Patch all you can – or be punished
UK data watchdog rolls up its sleeves, polishes truncheon
Ello? ello? ello?: Facebook challenger in DDoS KNOCKOUT
Gets back up again after half an hour though
SHELLSHOCKED: Fortune 1000 outfits Bash out batches of patches
CloudPassage points to 'pervasive' threat of Bash bug
prev story

Whitepapers

Providing a secure and efficient Helpdesk
A single remote control platform for user support is be key to providing an efficient helpdesk. Retain full control over the way in which screen and keystroke data is transmitted.
Intelligent flash storage arrays
Tegile Intelligent Storage Arrays with IntelliFlash helps IT boost storage utilization and effciency while delivering unmatched storage savings and performance.
Beginner's guide to SSL certificates
De-mystify the technology involved and give you the information you need to make the best decision when considering your online security options.
Security for virtualized datacentres
Legacy security solutions are inefficient due to the architectural differences between physical and virtual environments.
Secure remote control for conventional and virtual desktops
Balancing user privacy and privileged access, in accordance with compliance frameworks and legislation. Evaluating any potential remote control choice.