Stealthy Microsoft SQL Server Backdoor Malware Spotted in the Wild

Dubbed Skip-2.0, the backdoor malware is a
post-exploitation tool that runs in the memory and lets remote
attackers connect to any account on the server running MSSQL
version 11 and version 12 by using a “magic password.”

What’s more? The malware manages to remain undetected on the
victim’s MSSQL Server by disabling the compromised machine’s
logging functions, event publishing, and audit mechanisms every
time the “magic password” is used.

With these capabilities, an attacker can stealthily copy,
modify, or delete the content stored in a database, the impact of
which varies from application to application integrated with
targeted servers.

“This could be used, for example, to manipulate in-game currencies
for financial gain. In-game currency database manipulations by
Winnti operators have already been reported,” researchers said.

Chinese Hackers Created Microsoft SQL Server Backdoor

First documented by ESET earlier this month, PortReuse backdoor
is a passive network implant for Windows that injects itself into a
running process already listening on a TCP port, “reusing” an
already open port, and waits for an incoming magic packet to
trigger the malicious code.

Like other Winnti Group payloads, Skip-2.0 also uses encrypted
VMProtected launcher, custom packer, inner-loader injector and
hooking framework to install the backdoor, and persists on the
targeted system by exploiting a DLL hijacking vulnerability in a
Windows process that belongs to a system startup service.

Since the Skip-2.0 malware is a post-exploitation tool, an
attacker first needs to compromise targeted MSSQL servers to have
administrative privileges necessary to achieve persistence and
stealthiness.

“Note that even though MSSQL Server 11 and 12 are not the most
recent versions (released in 2012 and 2014, respectively), they are
the most commonly used ones according to Censys’s data,” the
researchers said.