Necessary Steps to Securing the WLAN Configuration According to NIST SP800-48 [11] (draft), network administrators need to configure APs in accordance with established security policies and requirements

Controlling the reset function. The reset function poses a particular problem because it allows an individual to negate any security settings administrators have configured in the AP. It does this by returning the AP to its default factory settings. The default settings generally do not require an administrative password and may disable encryption. An individual can reset the configuration to the default settings by simply inserting a pointed object such as a pen into the reset hole and pressing. If a malicious user gains physical access to the device, that individual can exploit the reset feature and cancel out any security settings on the device. The reset function, if configured to erase basic operational information such as an IP address or keys, can further result in a network denial-of-service (DoS), because APs may not operate without these settings. Having physical access controls in place to prevent unauthorized users from resetting APs can mitigate the threats. Organizations can detect threats by performing regular security audits.

Changing the SSID. The SSID of the AP should be changed from the factory default. Although an equipped adversary can capture this identity parameter over the wireless interface, it should be changed to prevent unsophisticated adversary attempts to connect to the wireless network.

Changing default cryptographic keys. The manufacturer may provide one or more keys to enable shared key authentication between the device trying to gain access to the network and the AP. Using a default shared key setting is a security vulnerability because many vendors use identical shared keys in their factory settings. A malicious user may know the default shared key and use it to gain access to the network. Changing the default shared key setting to another key will mitigate the risk. For example, the shared key could be changed to "954617" instead of using a factory default shared key of "111111." No matter what their security level, organizations should change the shared key from the default setting because it is easily exploited. In general, organizations should opt for strong encryption (e.g.,128-bit), regardless of their security levels, whenever it is available. If it is not available or feasible, organizations should, assuming they have already performed a risk analysis, use 40-bit encryption. Finally, a generally accepted principle for proper key management is to change cryptographic keys often.

Changing the default SNMP parameter. Some wireless APs use SNMP agents, which allow network management software tools to monitor the status of wireless APs and clients. The default SNMP community string that SNMP agents commonly use is the word "public" with assigned "read" or "read and write" privileges. Using this well-known default string leaves devices vulnerable to attack. If an unauthorized user were to gain access and had read/write privileges, that user could write data to the AP, resulting in a data integrity breach. Organizations that require SNMP should change the default community string, as often as needed, to a strong community string. Privileges should be set to "read only" if that is the only access a user requires. If SNMP is not required on the network, the organization should disable SNMP altogether.

Using DHCP. Automatic network connections involve the use of a Dynamic Host Control Protocol (DHCP) server. The DHCP server automatically assigns IP addresses to devices that associate with an AP when traversing a subnet. For example, a DHCP server is used to manage a range of TCP/IP addresses for client laptops or workstations. After the range of IP addresses is established, the DHCP server dynamically assigns addresses to workstations as needed. The server assigns the device a dynamic IP address as long as the encryption settings are compatible with the WLAN. The threat with DHCP is that a malicious user could easily gain unauthorized access on the network through use of a laptop with a wireless NIC. Because a DHCP server will not necessarily know which wireless devices have access, the server will automatically assign the laptop a valid IP address. Risk mitigation involves disabling DHCP and using static IP addresses on the wireless network, if feasible. This alternative, like the MAC ACL countermeasure, may only be practical for relatively small networks, given the administrative overhead involved with assigning static IP addresses and the possible shortage of addresses. Statically assigning IP addresses would also negate some of the key advantages of wireless networks, such as roaming or establishing ad hoc networks. Another possible solution is to implement a DHCP server inside of the wired network's firewall that grants access to a wireless network located outside of the wired network's firewall. Still another solution is to use APs with integrated firewalls. This last solution will add an additional layer of protection to the entire network. All users should evaluate the need for DHCP considering the size of their network.