Wireless local area network (WLAN) is used in many industries. The popularity owes to many reasons, like easy installation or mobility. Unfortunately, despite of the benefits, WLAN have some security threats, mentioned above, which anyone should be aware of.This paper begins with introduction to WLAN. The introductory section gives some information about characteristic, usage and advantages of WLAN. Next chapter will cover the wireless networking specification. This paper will also list down WLAN components and architecture. The most important sections will explain the key issues: security threats of WLAN and security best practices. The last chapter is dedicated to WPA2-Krack Security Issue – the bug, known as “KRACK” for Key Reinstallation Attack (discovered in November last year). Finally, this paper ends with the conclusion of highlighted issues and solutions.Introduction to WLANA wireless local area network (WLAN) is a local area network (LAN) that doesn’t rely on wired Ethernet connections – it links two or more devices using non cable communication within a limited area. It is used at home, school, computer laboratory or office building. A WLAN may be an extension to an existing cable network or an alternative to it. Wireless technology has helped to simplify networking, avoiding additional or unwanted wiring, drilling into walls or stringing Ethernet cables all over a building. These resources might include a broadband Internet connection, network printers, data files and audio/video streaming.Since the ratification of the IEEE (Institute of Electrical and Electronics Engineers) 802.11b standard in 1999, wireless LANs have become more dominant. Today, wireless LANs are widely deployed in places like corporate offices, conference rooms, Internet-ready classrooms and even coffeehouses.Wireless networking offers the same capabilities and speeds comparable to a wired 10BASE-T network without the difficulties associated with laying wire, drilling into walls, etc. Laptop users have the freedom to connect anywhere in the building. Every room in a wireless home or office can be connected to the network, so growing a network and adding more users can be as simple as installing a new wireless network adapter.WLANs have data transfer speeds ranging from 1 to 54Mbps (some manufacturers offers 108Mbps solutions). The 802.11n standard can reach 300 to 600Mbps.A WLAN signal can be broadcast to cover an area ranging in size from a small office to a large campus. Most commonly, a WLAN access point provides access within a radius of 20 to 90 meters.Reasons to choose wireless networking over traditional wired networks include: no need to add more wires or drill new holes in a home or office, because of comfort or rental regulations; infrastructure limitations; too big costs. Sometimes network access is needed outside the building.Because the wireless signal is broadcast, so everybody nearby can share it. Several security protection methods are necessary to ensure only authorized users can access WLAN.