Hackers exploit a blind spot by hiding malware inside DNS records

Hackers are stashing malware in a place that's largely out of the reach of most defenses-inside domain name system (DNS) records that map domain names to their corresponding numerical IP addresses.

The practice allows malicious scripts and early-stage malware to fetch binary files without having to download them from suspicious sites or attach them to emails, where they frequently get quarantined by antivirus software. That's because traffic for DNS lookups often goes largely unmonitored by many security tools. Whereas web and email traffic is often closely scrutinized, DNS traffic largely represents a blind spot for such defenses.

A strange and enchanting place

Researchers from DomainTools on Tuesday said they recently spotted the trick being used to host a malicious binary for Joke Screenmate, a strain of nuisance malware that interferes with normal and safe functions of a computer. The file was converted from binary format into hexadecimal, an encoding scheme that uses the digits 0 through 9 and the letters A through F to represent binary values in a compact combination of characters.

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