WiFinder is a battery powered, portable network analyzer that detects wireless computer networks using the ubiquitous 802.11 standard. Relevant network information is provided to the user, including the SSID, security type, access point manufacturer, MAC address, and more. The device uses a compact flash network card for a wireless interface. The collected information is presented to the user on a 1.8″ color LCD. A directional joystick interface is provided for device navigation. The main feature of WiFinder is its passive detection method, as opposed to active detection. Active network detection requires the sniffing device to attempt connection to the remote access point to successfully find a network, allowing other network users or administrators to detect the presence of a sniffer. Passive network detection allows the sniffing device to remain undetectable. This is accomplished by disabling transmissions, and instead analyzing all packets sent to every network node in range. Logging of detected networks to a SD flash card is also supported. This version used a Microchip PIC 18F series chip. Later on, I designed another version using an ARM7 chip to increase packet analysis speed.