ISL Internet Sicherheitslösungen GmbH, based in Bochum, Germany, is a leading German software manufacturer in the field of IT security with a focus on network access control (NAC). ISL was founded in 1999 by Dr. Andreas Rieke. As early as 2003, ISL was one of the first companies worldwide to develop and sell software solutions for network access control. Well-known companies from industry, trade, banks, public authorities and research institutes rely on ISL's ARP-GUARD software to protect their IT infrastructure against internal attacks as well as unnoticed intrusion of unauthorized devices.