It requires the patch described here:
I did not test with WEP encryption, and would not be surprised if it did not work, but mac filtering should work just fine.
Edit: Infrastructure mode and not ad-hoc mode now works with liberated_aria_R003. Encryption is also confirmed working.
I use this version with R003: wireless_tether_2_0_5-pre8.apk
And I use this bin extracted and placed into a folder called android.tether in the root of the sdcard : http://www.mediafire.com/?h4wmvi9iwdvextv
Note: The folder name MUST be exactly android.tether - and as all things Linux, it is case sensitive.
Note: if you use this, please consider donating to support the project. You can find the link on the project homepage here: