Cracking Wireless Netwrok : By airmon-ng in LINUX

WEP was intended to provide comparable confidentiality to a traditional wired network (in particular it does not protect users of the network from each other), hence the name. Several serious weaknesses were identified by cryptanalysts — any WEP key can be cracked with readily available software in two minutes or less — and WEP was superseded by Wi-Fi Protected Access (WPA) in 2003, and then by the full IEEE 802.11i standard (also known as WPA2) in 2004. Despite the weaknesses, WEP provides a level of security that can deter casual snooping.

It’s fairly easy to crack a WEP encrypted wireless network. Infact the WEP encryption has some serious flaws in its design, flaws that make it easy and fast to crack or hack.
Install aircrack-ng