I w as testing the security of my wifi network following this guide and I am using "RTL8191SU 802.11n WLAN Adapter" in my debian pc for this purpose.
iwconfig lists :
lo no wireless extensions. wlan0 unassociated Nickname:"rtl_wifi" Mode:Managed Access Point: Not-Associated Sensitivity:0/0 Retry:off RTS thr:off Fragment thr:off Power Management:off Link Quality:0 Signal level:0 Noise level:0 Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:0 Tx excessive retries:0 Invalid misc:0 Missed beacon:0 eth0 no wireless extensions.
when I try to put it into monitor mode by issuing ,
sudo iwconfig wlan mode monitor , i get :
Error for wireless request "Set Mode" (8B06) : SET failed on device wlan ; Operation not permitted.
and when I issue ,
sudo airmon-ng start wlan0:
Found 4 processes that could cause trouble. If airodump-ng, aireplay-ng or airtun-ng stops working after a short period of time, you may want to kill (some of) them! PID Name 1794 avahi-daemon 1795 avahi-daemon 2174 NetworkManager 2858 wpa_supplicant Interface Chipset Driver
I have'nt installed any drivers for the same and yet I can connect to my wifi access point and surf Internet without any trouble using this device but couldn't complete the above procedure.
What may be the reason for the same ? And How to fix it ?