Telhack
Telhack was a group of young computer enthusiasts or hackers from Sweden, active in the early 2000's. They released a number of novice tutorials on various hacking- and phreaking related subjects as well as a few security advisories, exploits, trojan horses/RATs and more. Today, Telhack is merely an IRC chatroom located on EFnet.
A few releases: Backdoor.Hatckel, d0ped Trojan, Shambala Server 4.5 (Security Advisory and PoC Exploit), Blackmoon FTP Server 2.6 (Security Advisory), PVote 1.5 (Security Advisory), IcrediBB 1.1 (Security Advisory), Flooder.Win32.TelHack, Bindcheck (BIND-scanner for *nix/*BSD), Cloning with Sim-Pic v 2.4 (Tutorial), Breaking in to Mobiflex (Tutorial), General SS7 Security (Tutorial), Exploiting PHP (Tutorial), UAV_MOPS/Military Radio Warfare (Tutorial).