![]() And failing that, force the issue by sending disassociation frames forcing the clients to re-probe, but there is ample material on this elsewhere on the internet. Then focus our efforts on only that single channel, greatly decreasing the time required to capture a probe response. Of course, if we were doing this for a purpose other than learning, we would first find the channel on which the hidden SSID was being broadcast. ![]() This is easier to achieve with a larger number of clients, but it may take longer with only one test client. As probe responses are dependent on clients sending probe requests, this means the stars need to align (not really) and the probe response to the client needs to be sent while listening on that specific channel. First, we need to catch a beacon, then, we also need to catch a probe response on the same channel. One caveat here, when scanning on all channels the process may take some time. If there is a match, we use the SSID from the probe response, instead of the null value from the beacon. If the standard beacon does not contain an SSID value, we check for the SSID in the list of probe responses. One entry (the last received) will be kept for each BSSID. That’s all there really is to it, the tool will maintain a mapping of all BSSIDs and SSIDs received from probe responses. IF same BSSID exists in new dictionary (created from probe response) Retrieve the SSID from the beacon as before ![]() Please refer to the previous post for the rest of the code.Īdditional Pseudocode For each received frame Using this as a base, we only need to add a bit of new logic to show the hidden SSIDs. In the previous post titled Building a Wi-Fi scanner with Scapy we built a simple wireless discovery tool. The image below shows a (manually configured) client sending a probe request to an AP, with the name of the (hidden) SSID, and the AP responding with a probe response, also with the name of the SSID.Īll this means is that if we need to learn the SSID we just have to look at the probes instead of the beacons. Having a look at the mechanism itself, we can see that while the SSID is indeed removed from the beacon, it still exists in other frame exchanges. There are additional downsides to hidden SSIDs including possible issues with client roaming. Not advertising the SSID in the beacon is not the correct mechanism for reducing the number of beacons, only reducing the number of SSIDs will do that.Ĭonnecting a client to a hidden SSID requires prior knowledge of the SSID name as the client is unable to discover the network automatically, putting an additional burden of the network administrator to pre-configure all the devices. If the hiding of the SSID has been implemented as a measure to reduce the number of advertised SSIDs, then resolving this issue becomes a little more complicated. A common recommendation is to have no more than four SSIDs for a standard deployment, and less (just one) in the case of very high-density deployments. Having too many SSIDs increases the number of beacons and management overhead, and reduces available channel capacity. Recall that each wireless network uses precious airtime simply for advertising the network, typically through beacons. hidden SSIDs are sometimes used (incorrectly) as a workaround for having too many SSIDs. The reason could also be a little more convoluted, e.g. It could be a simple case of “we thought it would be secure” which can be remedied by implementing the necessary security mechanisms, such as WPA2/3. When working on a network that is configured to not broadcast the SSID, it is important to understand the reasons behind the configuration. Hidden SSIDs are still a common occurrence in some commercial deployments today. It holds no significant value as a security mechanism, nor should it be considered a security mechanism, and actually has a couple of disadvantages which can outweigh the benefit of using it. Hiding the SSID is useful only as a mechanism for protecting against casual onlookers. The basic idea is that if the SSID name is not advertised, no one will know about the wireless network, but this is not entirely true. ![]() Hiding of the SSID is a common feature available in most wireless systems. The topic today is hidden SSIDs and some misconceptions about the benefits. ![]()
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