The service set identifier (SSID) is meant to differentiate networks from one another. The default SSID should be changed on all access points having a default SSID. Access points are often set to a default SSID when they are first purchased. For example, most Linksys access points are set to the network name of linksys, most early Cisco access points had a default SSID of tsunami, most Netgear access points are set to netgear, and so on. These default SSIDs are widely documented on the Internet and are well known by any cracker. The fact that the SSID is still set to the default is often a glaring banner to the attacker that reads, “Please attack me as I am still configured to all default settings!” While it may not be true that “all” settings are still at their defaults, let’s just say there is a very good chance.
When access points are first installed, the SSID should be changed to something cryptic and not something that could be used to determine the company to whom the access point belongs. This recommendation assumes that other companies may be nearby. If no other companies are nearby, the attacker can assume that any visible SSID with a good signal strength is the local company’s network. Changing the SSID to something meaningful such as a department name can provide an intruder valuable information. For example, if a wireless network is installed for the accounting department, and you set the SSID to accounting, any intruder will know there could be financial information on the network to which the access point is attached. However, with all that being said, proper security makes it all a moot point – and you should have proper security (WPA2-Personal or WPA2-Enterprise these days).
Some wireless security professionals will suggest that you set the SSID according to strong password principles. I disagree with this suggestion as it implies that the SSID somehow affords security itself. While you can give away too much information about the intent of the network with the SSID name (such as in the accounting department example in the preceding paragraph), you cannot really ensure security through what you might call a cryptic SSID or a strong SSID. Skilled attackers can find and access a wireless network that has no security other than a cryptic SSID very easily. Ultimately, I suggest you use the SSID for its intended purpose: to differentiate between networks and not to provide security.
By default, an access point broadcasts the SSID several times per second in beacons (10 times for most standards-based implementations). By listening for these beacons, intruders are provided the opportunity to gather the SSIDs of any access point within range. “Closing the system” by not broadcasting SSIDs in beacons prevents intruders from passively locating the network. Closed system features are not part of the 802.11 series of standards and they are not supported on all access points. When SSIDs are not broadcast, operating systems like Windows XP do not automatically discover the SSID. This configuration causes a potential intruder to put forth a little more effort to gain access to the network—something an intruder may not be willing to do. Unless your organization is protecting something that a cracker knows is valuable, most crackers will attack the “low hanging fruit” first, meaning that any networks that are broadcasting an SSID will be the first targets for intrusion.
However, even when SSID broadcasting is disabled, the SSID can be discovered using utilities that perform active scanning (sending probe request frames) or wireless packet analyzers (which hear all frames types). Sometimes disabling SSID broadcasting may go against business goals, such as with public wireless networks. These networks must be open to allow customers to easily access network resources (usually Internet access). In the end, again, use the SSID for network differentiation and not for security.
Now, to be clear, you can certainly have different security settings associated with different SSIDs, but this is not the same thing as saying that SSIDs give you security. They do not. Can we rid ourselves of this thinking once and for all? I hope so.
SUMMARY: Use the SSID attribute to provide organizational structure to your wireless network and as an indicator to your users as to what network they are accessing. Do not use it as a security solution.