SKHack denotes the July 2011 intrusion into SK Communications that exposed personal information belonging to as many as 35 million CyWorld and Nate users. Attackers compromised more than 60 employee computers by redirecting software-update traffic to a counterfeit server and delivering a trojanized update, then used the infected systems to reach customer databases. The operation also relied on legitimate third-party infrastructure to host tools and deployed a disguised remote-access Trojan as a service, combining supply-chain-style trust abuse, persistence, obfuscated strings, and remote control in a carefully prepared targeted breach.