How can I tell if my computer's been accessed by someone else, and how do I prevent it?

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If you really want to be secure, get an advanced firewall that will block EVERYTHING first, and then learn through dialogs sent to you for each application/user/port that tries to access your machine.

Windows Update uses service files for example that connect to the internet to check for updates. Most firewalls will not warn you of this. An Advanced firewall will ask you to give every file permission permanently or just for this session. Even the simple update for your clock requires certain service files to access the internet. You will be prompted about everything...

The downside to this, is that you must have extensive knowledge of exactly what services/files/ports you should be letting through, and which you should not... For example, some random .dll might be asking you for permission to access the internet and you would chose no because you dont know what it is... Later you find out that your clock never updated to modify the new daylights savings time because you never received the hotfix from windows update... You have to know what does what and when to let it through..

Be wary though, software firewalls have to search the header of every single packet that comes in to find a port number. If you have a lot of data coming in and out, a software firewall will give your CPU a workout.. Possibly 15%-30% CPU usage on a decent connection on full load. You chose if it's worth it..

Under the Start fly-up is Recent Documents.
I was thinking if I did not access the most recent documents listed...........Then someone else must have turned on my computer and and accessed my docs. Yes or No

dear Leo,
how realible is the internet explorer hitory? if I see that a document has been accessed during my vacation, how can that be ? could it be a mistake? am I beeing hacked ? thanks, L.S.

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I wouldn't suspect a hack. I think someone just used your computer while you were away.

Leo

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Thanks for the answer. I also checked the event viewer. It showed some activity during that same period I was away. But apparently nobody had access to me house.
So basically the event viewer and IE History are showing that someone has used the Computer, but nobody was there!? Are those (History and event viewer) reliable? Because you said before " sadly there really isn't a practical way to determine if your computer has been accessed"
If yes, i need to protect my home. I am desperate.
Thanks for your help.

Leo,Thank you so much for your answer! Sorry for this late reply. I just found your email in my box tonight. I was so surprised and happy to know that you have answered my question. I really appreciate that you explained everything so well,in details and that you cared to answer all my questions one by one.

Your answer is so clear and easy to understand although it covers a good range of complicated issues. Now I do understand more about internet and internet security because of your great help. I am going to make some changes according to your advice.

I am very grateful. You are great, Leo!!

Hello Leo,
this is my first time to read Your articles, I'm from Croatia, studying informatics, and I think that this theme is very interesting.
I'm not best in English but I have some questions, so please can You answer me :
1. I have ZoneAlarm free firewall. What did You mean by Advanced firewall, or Hardware firewall, because my computer is significantly slowed down, like You said beacuse of my software firewall. And in the last 2 weeks I reinstalled my WinXP 5 times because of trojans and other spyware. I had Avast but now I switched to NOD32 plus Adaware 2007.
2. I have D-Link wireless ADSL 2+ Router (DSL-G684T) and I would like to change the ip address so that only me and my roomate can access the router. We don't even use wireless cards, we are connected to the router with cables. Antenna is also switched from router. Can anyone other now access our internet connection, because we can download 1Gb/month (I know it's silly for US standards) and don't want someone else to use it. And how to turn on that WEP, will it ask me for a password if it's turned on?

Thank You

hello im not sure whats going on. my computer acts like someone else is doing something on the other end of my computer.everytime i log on a message comes on telling me that windows internet explorer has to abort! this happens (every time)!i have scanned it and it tells me all is fine i am the (only one) who uses this computer so i dont understand what is going on can you help me thanks!

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You haven't given a lot of details to go on, but perhaps
this article might be a start:
http://ask-leo.com/iexploreexe_has_generated_an_error_now_what.html

Leo

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I think my husband has somehow managed to get shared access to my computer to check up on me. My comp crashed last week losing all my work stuff he rebooted and swore he did nothing but Im pretty sure he loaded something again....Please help!!!!

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