With Arma 2 came along the option for players to cheat by holding left shift and the numpad minus key. This can be abused as it is a backdoor to complete the backpack dupe, for which most servers have a fix for. To fix this, it's very simple:
1. Open up dayz_spaceInterrupt.sqf
2. Find the following:
_shift = _this select 2;
_ctrl = _this select 3;
_alt = _this select 4;
And paste the following below:
if (_shift) then {
if(_dikCode == 0x4A) then {
execVM "PAT