If it's the same as the 405 there was a special tool for cable boxes that took them out. I have been told you can get them out with pliers and replace them with a Phillips head screw. I know the 920 uses tamper proof torx but not my 405.
If you go to an electronics supply like MCM electronics these are sold in a set and have the torx driver center drilled out called a security driver set. I use them often. I have changed batteries on 4DTV and DSR-4200 receivers with out a mishap . The 4200 batteries were 13 and 14 years old and showed full voltage. Did not want to take a chance but think these 10 year batteries[Maxwell super] would last 20 years.
You can use side cutter pliers, turn them on end putting the pointy tips in the little slots on sides of screws and give a twist. Regular size side cutters will work but the half size ones work best, I believe they are move for smaller electronic work