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Information About Rogue Devices
Rogue access points can disrupt wireless LAN operations by hijacking legitimate clients and using plain-text or other denial-of-service or man-in-the-middle attacks. That is, a hacker can use a rogue access point to capture sensitive information, such as usernames and passwords. The hacker can then transmit a series of Clear to Send (CTS) frames. This action mimics an access point, informing a particular client to transmit, and instructing all the other clients to wait, which results in legitimate clients being unable to access network resources. Wireless LAN service providers have a strong interest in banning rogue access points from the air space.
Because rogue access points are inexpensive and readily available, employees sometimes plug unauthorized rogue access points into existing LANs and build ad hoc wireless networks without their IT department's knowledge or consent. These rogue access points can be a serious breach of network security because they can be plugged into a network port behind the corporate firewall. Because employees generally do not enable any security settings on the rogue access point, it is easy for unauthorized users to use the access point to intercept network traffic and hijack client sessions. Even more alarming, wireless users frequently publish unsecure access point locations, increasing the odds of having enterprise security breached.
The following are some guidelines to manage rogue devices:
The containment frames are sent immediately after the authorization and associations are detected. The enhanced containment algorithm provides more effective containment of ad hoc clients.
In a dense RF environment, where maximum rogue access points are suspected, the chances of detecting rogue access points by a local mode access point in channel 157 or channel 161 is less when compared to other channels. To mitigate this problem, we recommend that you use dedicated monitor mode access points.
The local mode access points are designed to serve associated clients. These access points spend relatively less time performing off-channel scanning: about 50 milliseconds on each channel. If you want to perform high rogue detection, a monitor mode access point must be used. Alternatively, you can reduce the scan intervals from 180 seconds to a lesser value, for example, 120 or 60 seconds, ensuring that the radio goes off-channel more frequently, which improves the chances of rogue detection. However, the access point will still spend about 50 milliseconds on each channel.
Rogue detection is disabled by default for OfficeExtend access points because these access points, which are deployed in a home environment, are likely to detect a large number of rogue devices.
Client card implementations might mitigate the effectiveness of ad hoc containment.
It is possible to classify and report rogue access points through the use of rogue states and user-defined classification rules that enable rogues to automatically move between states.
Each controller limits the number of rogue containments to three per radio (or six per radio for access points in the monitor mode).
Rogue Location Discovery Protocol (RLDP) detects rogue access points that are configured for open authentication.
RLDP detects rogue access points that use a broadcast Basic Service Set Identifier (BSSID), that is, the access point broadcasts its Service Set Identifier in beacons.
RLDP detects only those rogue access points that are on the same network. If an access list in the network prevents the sending of RLDP traffic from the rogue access point to the controller, RLDP does not work.
RLDP does not work on 5-GHz dynamic frequency selection (DFS) channels. However, RLDP works when the managed access point is in the monitor mode on a DFS channel.
If RLDP is enabled on mesh APs, and the APs perform RLDP tasks, the mesh APs are dissociated from the controller. The workaround is to disable RLDP on mesh APs.
If RLDP is enabled on nonmonitor APs, client connectivity outages occur when RLDP is in process.
If the rogue is manually contained, the rogue entry is retained even after the rogue expires.
If the rogue is contained by any other means, such as auto, rule, and AwIPS preventions, the rogue entry is deleted when it expires.
The controller will request to AAA server for rogue client validation only once. As a result, if rogue client validation fails on the first attempt then the rogue client will not be detected as a threat any more. To avoid this, add the valid client entries in the authentication server before enabling Validate Rogue Clients Against AAA.
In the 7.4 and earlier releases, if a rogue that was already classified by a rule was not reclassified. In the 7.5 release, this behavior is enhanced to allow reclassification of rogues based on the priority of the rogue rule. The priority is determined by using the rogue report that is received by the controller.
Detecting Rogue Devices
The controller continuously monitors all the nearby access points and automatically discovers and collects information on rogue access points and clients. When the controller discovers a rogue access point, it uses the Rogue Location Discovery Protocol (RLDP) to determine if the rogue is attached to your network.
You can configure the controller to use RLDP on all the access points or only on the access points configured for the monitor (listen-only) mode. The latter option facilitates automated rogue access point detection in a crowded radio frequency (RF) space, allowing monitoring without creating unnecessary interference and without affecting the regular data access point functionality. If you configure the controller to use RLDP on all the access points, the controller always chooses the monitor access point for RLDP operation if a monitor access point and a local (data) access point are both nearby. If RLDP determines that the rogue is on your network, you can choose to contain the detected rogue either manually or automatically.
A rogue access point is moved to a contained state either automatically or manually. The controller selects the best available access point for containment and pushes the information to the access point. The access point stores the list of containments per radio. For auto containment, you can configure the controller to use only the monitor mode access point.
The containment operation occurs in the following two ways:
The container access point goes through the list of containments periodically and sends unicast containment frames. For rogue access point containment, the frames are sent only if a rogue client is associated.
Whenever a contained rogue activity is detected, containment frames are transmitted.
Individual rogue containment involves sending a sequence of unicast disassociation and deauthentication frames.
Cisco Prime Infrastructure Interaction and Rogue Detection
Cisco Prime Infrastructure supports rule-based classification and uses the classification rules configured on the controller. The controller sends traps to Cisco Prime Infrastructure after the following events:
If an unknown access point moves to the Friendly state for the first time, the controller sends a trap to Cisco Prime Infrastructure only if the rogue state is Alert. It does not send a trap if the rogue state is Internal or External.
If a rogue entry is removed after the timeout expires, the controller sends a trap to Cisco Prime Infrastructure for rogue access points categorized as Malicious (Alert, Threat) or Unclassified (Alert). The controller does not remove rogue entries with the following rogue states: Contained, Contained Pending, Internal, and External.
How to Configure Rogue Detection
Configuring Rogue Detection (CLI)
2. wireless wpsroguedetectionmin-rssirssi in dBm
3. wireless wpsroguedetectionmin-transient-time time in seconds
Specify the minimum RSSI value that rogues should have for APs to detect and for rogue entry to be created in the controller.
Valid range for the rssi in dBm parameter is –128 dBm to -70 dBm, and the default value is -128 dBm.
This feature is applicable to all the AP modes. There can be many rogues with very weak RSSI values that do not provide any valuable information in rogue analysis. Therefore, you can use this option to filter rogues by specifying the minimum RSSI value at which APs should detect rogues.
wireless wpsroguedetectionmin-transient-time time in seconds
Specify the time interval at which rogues have to be consistently scanned for by APs after the first time the rogues are scanned.
Valid range for the time in sec parameter is 120 seconds to 1800 seconds, and the default value is 0.
This feature is applicable to APs that are in monitor mode only.
Using the transient interval values, you can control the time interval at which APs should scan for rogues. APs can also filter the rogues based on their transient interval values.
This feature has the following advantages:
Rogue reports from APs to the controller are shorter
Transient rogue entries are avoided in the controller
Unnecessary memory allocation for transient rogues are avoided
Returns to privileged EXEC mode. Alternatively, you can also press Ctrl-Z to exit global configuration mode.
Configuring Rogue Detection (GUI)
Make sure that rogue detection is enabled on the corresponding access points. Rogue detection is enabled by default for all access points joined to the controller (except for OfficeExtend access points). However, you can enable or disable rogue detection for individual access point by choosing Configuration > Wireless > Access Policies > All APs to open Edit AP page, selecting or unselecting the Rogue Detector check box in the General area of the Edit AP page.
Choose one of the following options from the Rogue Location Discovery Protocol drop-down list:
Disable—Disables RLDP on all the access points. This is the default value.
All APs—Enables RLDP on all the access points.
Monitor Mode APs—Enables RLDP only on the access points in the monitor mode.
In the Expiration Timeout for Rogue AP and Rogue Client Entries text box, enter the number of seconds after which the rogue access point and client entries expire and are removed from the list. The valid range is 240 to 3600 seconds, and the default value is 1200 seconds.
If a rogue access point or client entry times out, it is removed from the controller only if its rogue state is Alert or Threat for any classification type.
To use the AAA server or local database to validate if rogue clients are valid clients, select the Validate Rogue Clients Against AAA check box. By default, the check box is unselected.
If necessary, select the Detect and Report Adhoc Networks check box to enable adhoc rogue detection and reporting. By default, the check box is selected.
In the Rogue Detection Report Interval text box, enter the time interval, in seconds, at which APs should send the rogue detection report to the controller. The valid range is 10 seconds to 300 seconds, and the default value is 10 seconds.
If you want the controller to automatically contain certain rogue devices, enable the following parameters. By default, these parameters are in disabled state.
When you select any of the Auto Contain parameters and click Apply, the following message is displayed: “Using this feature may have legal consequences. Do you want to continue?” The 2.4-GHz and 5-GHz frequencies in the Industrial, Scientific, and Medical (ISM) band are open to the public and can be used without a license. As such, containing devices on another party’s network could have legal consequences.
Auto Containment Level—Set the auto containment level. By default, the auto containment level is set to 1.
Auto Containment only for Monitor mode APs—Configure the monitor mode access points for auto-containment.
Rogue on Wire—Configure the auto containment of rogues that are detected on the wired network.
Using Our SSID—Configure the auto containment of rogues that are advertising your network’s SSID. If you leave this parameter unselected, the controller only generates an alarm when such a rogue is detected.
Valid Client on Rogue AP—Configure the auto containment of a rogue access point to which trusted clients are associated. If you leave this parameter unselected, the controller only generates an alarm when such a rogue is detected.
Adhoc Rogue AP—Configure the auto containment of adhoc networks detected by the controller. If you leave this parameter unselected, the controller only generates an alarm when such a network is detected.
Click Save Configuration.
Monitoring Rogue Detection
This section describes the new command for rogue detection.
The following command can be used to monitor rogue detection on the controller.
Table 1 Monitoring Rogue Detection Command
show wireless wps rogue ap summary
Displays a list of all rogue access points detected by the controller.
show wireless wps rogue client detailedclient-mac
Displays detailed information for a specific rogue client.
Examples: Rogue Detection Configuration
This example shows how to configure the minimum RSSI that a detected rogue AP needs to be at, to have an entry created at the
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