Backdoor on my laptop?

[joco1500]

Hello all.

I have a old-ish Dell laptop and put Ubuntu 11.10 on it. Works great. It is as fast as my windows 7 laptop that i use for school. But i let my friend use my Ubuntu laptop and he is kinda a douche. He is a computer guy and i think that he put a backdoor on my laptop. I keep finding things lost and other things downloaded and things in other folders when i go to use them.

I just want a way to find it and i don't want smart-*** responses.
I just want to get my computer fixed and maybe i might put a backdoor on his windows xp set up.

[Gster4]

did this guy have root access?
use the system monitor and look for weird proccess running.

[CharlesA]

Did he use the machine under your user or as guest?

If he logged in as your user, he could run anything as your user and mess with anything in your home directory.

[drawkcab]

reinstall.

[squakie]

reinstall.

+1. Your description makes it sound like a lot of things are screwed up - there isn't a single answer we can give you. I would suggest you back up any data you want to save, then do as drawcab said and resintall - perhaps even with 12.04lts.

[hydn79]

+1 reinstall AND tired of saying this to people... enable the BIOS password guys!!!

I don't use Linux password, just BIOS password which pops up BEFORE it boots from any drives, or boot media.

[offgridguy]

reinstall.

+1

[d4rk0wl]

I don't use Linux password, just BIOS password which pops up BEFORE it boots from any drives, or boot media.

Agreed, it is a good measure of security that way nobody can boot off of a USB and tamper with various system files on drive.

[mastablasta]

I don't use Linux password, just BIOS password which pops up BEFORE it boots from any drives, or boot media.

that's just silly! basically you closed your computer so noone bot you can boot it. on the other hand once you boot into it you opened up to internet and malware.

linux password is there to identify to computer that the person with admin rights is trying to change system files and not some malware. as you removed this security layer you basically "said": "anything can automaticly run on my mashcine, even malware. it doens't need my permission. and i give it full root access to my computer and data."

does that seem like a good idea?

win98 was running like that and most newer preinstalled windows do that by default the result is - plenty of infections in that OS.

[NikTh]

mastablasta , maybe hydn79 means that he/she is using the autologin feature (in login screen). Because I'm not very sure , but I think you cannot even install Ubuntu if you don't set a password.

Password is needed to install software and you cannot leave the password blank , because you will have problems. On the other hand , if you are an experienced user and you hacked the sudores file with NOPASSWD , then is up to you.

As for the BIOS password and/or root password , these are extra security that someone can take against a guy that he/she not trust with the PC powered on, in his hands.
BIOS password will prevent him to boot from a live media and root password will prevent him to boot into recovery mode and use the root console.

As for the OP , well... we don't know how much damage did this guy , so better would be to re-install.