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About running 2 anti-virus programs.

by CIT-IT / April 11, 2012 1:33 AM PDT

I recently purchased a Dell T1600 64-bit computer running Windows 7 Pro, which came with a Trend-Micro Worry-Free Business Security for 36 months. This is the 10th computer that I've ordered for my organization like this and have had no problems. But recently a new tech set this one particular unit up and installed AVG Free security software on this unit,(Why? I don't know!) then brings the unit back to me saying that it is not working properly and should be returned. After informing him that you cannot have 2 AV programs running in the background I am asked to provide proof. So I ask you my fellow Cnet people. Help by giving your comments so that I don't have to go digging thru all my junk at home to find that first Basic Computer Book from my 1st yr. of schooling. Thanks.

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Clarification Request
Common knowledge
by Willy / April 11, 2012 3:02 AM PDT

Many of the better AV pgms. provide protection in many aspects of PC operations. If they're doing their job it can be intensive "watchdog" of all your PC going on. In this aspect dual install of AV simply step on each other to provide the same services. In fact some AV pgms. upon finding another AV, may "disable" or reduce their effective operation regardless, so it has the sole task of providing protection. Even when AV pgms. are working for the time being it can easily fall in dispute and cause issues of their own nature. Further, the system resources can be hogged and thus reduced for PC operations when needed. It has always been good advice not to install similar AV protection. However, there are times when one area of protection can be allowed to work in lieu of the what maybe provided only because it is optional and I find "firewalls" are a good example of this.

To better resolve the issue just visit the Av support website and they in turn usually suggest the same advise. Further because provided AV is free for 36mos. no need to defeat it;s use.

tada ----Willy Happy

All Answers

Best Answer chosen by CIT-IT

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Turn it around
by MarkFlax Forum moderator / April 11, 2012 3:18 AM PDT

I would ask him to prove why we "should have" two or more anti-virus scanners running in the background.

It would seem he has already shown that running two AVs on this computer doesn't work, unless he is reluctant to provide his own proof by removing one and showing that it makes no difference to the performance of this computer. Let him do that if he is so confident.

Also, ask him if he is going to explain to the supplier that he has installed a 2nd AV on this system and he is not satisfied with its performance.

If you need proof yourself, then there is plenty around, for example; and

The sign of a good IT person is one who is willing to learn and admit his mistakes. Does he consider himself a good IT rep?

I hope that helps.


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My sentiments exactly! Thank You Mark
by CIT-IT / April 11, 2012 5:41 AM PDT
In reply to: Turn it around

Thank you for the quick responce. I knew I could count on my CNET people, I will not only forward this information on to the NEWBY but I will also recommend that he becomes a CNET subscriber, and if he already is one, I'll suggest that he perhaps should refer to it before he adamently defends his position. Thanks again.

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Newbie answer
by TheAncient / April 12, 2012 8:00 AM PDT

Here is an explanation suitable for a newbie. (I answered a similar question - involving 3 AV programs - in another forum)

The problem is the "real-time" component of the antivirus programs. What can happen is this:
- You want to access a file - let's say a Word document
- Virus program 1 says "Let me check this file first" - but that check is, in itself, an access
- Virus program 2 comes along and says "Hey virus program 1, before you get to open the file, I want to make sure it's safe" - again, this is another attempt to access the file.
- Virus program 3 then says "Virus program 2, you're not allowed to open the file before I check it" and virus program 3 proceeds to try to open the file.
- At this point, virus program 1 says "Virus program 3, let me check the file first just to make sure it's safe"
...and this goes on to the point where the entire machine freezes
SO: It is not a good idea to have the real-time component of multiple virus checkers enabled but it IS a good idea to run periodic checks of your computer with multiple antivirus programs. For example, on one of my machines I run AVG with real-time protection enabled and, on a monthly basis, I run Malwarebytes Antimalware and Superantispyware.

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Good answer but,
by mrmacfixit Forum moderator / April 12, 2012 9:08 AM PDT
In reply to: Newbie answer

don't let's confuse Anit-virus programs with Anti-Malware and Anti-Spyware programs.


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You're right but,
by TheAncient / April 12, 2012 11:01 AM PDT
In reply to: Good answer but,

You are correct, both "periodic" programs mentioned in my post are primarily anti-malware programs (even though they supposedly will catch viruses). The main point of my post was, to explain - to a lay person - why the real-time components of multiple anti-virus programs tend to "step on each other" and to point out that periodic checks (non-real-time) are ok.

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and your point was well made.
by mrmacfixit Forum moderator / April 12, 2012 10:03 PM PDT
In reply to: You're right but,

I just didn't want the lay person to think that Malwarebytes and SAS would be sufficient to catch the viruses.


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Dont uninstall Trend-Micro before uninstalling AVG!
by CKinVA / April 30, 2012 3:38 AM PDT

Because anti-virus & firewall programs must intercept fundimental system calls (i.e.: disk I/O's, browser/network events, etc.) to perform their checks they must add 'hooks' into the OS at a very basic level ... in fact, they may actually replace registry entries and/or .DLL's, .EXE's, etc, in the operating system's root libraries (i.e.: Win-7 runtime files).

When a second anti-virus program is installed (i.e.: AVG) it will want to catch many of the the same events; thus, it will undoubtably alter some of the 'hooks' (files, etc) that were already altered/replaced by the first anti-virus program (i.e.: Trend-Micro).

If you uninstall the first anti-virus program (i.e.: Trend-Micro) without having uninstalled the second one (i.e.: AVG), the uninstall process may actually overlay some of the 'hooks'/files/etc just (re)altered by AVG with what Trend-Micro saved off (the original OS settings & files); thus, hosing over both AVG and Win-7 ... you'll end up with a mix of things altered for AVG and things AVG expects to be altered but that are now back to the original Win-7 settings. Net result: You may to have to re-install the whole OS to get back to a fully functioning OS!

The same can happen regarding firewalls (and any other software that requires tight intregration into the OS). Two (or more) at a time can be very, very dangerious come uninstall time and they can also compete for resources and/or 'confuse' each other, etc, when both are running. For instance: "Deadly Embraces" (system lock-ups) can occur when both products try to handle the same event at the same time, etc.

So ... to be safe, fully uninstall an undesired product (& make sure your system still works propertly) before you install a replacement product ... This is a very good rule of thumb for all (replacement) software product installs actually.

Since you already have both Trend-Micro & AVG installed, I suggest you uninstall them in the reverse order installed and then re-install only the one you want (i.e.: uninstall AVG, reboot, check out system, if OK uninstall Trend-Micro, reboot, check out system, if OK install AVG).

1) It is not a bad idea to create a recovery point before/after any anti-virus/firewall/etc install either.
2) Most anti-adware/spyware programs do not alter the OS, etc, UNLESS they also have a 'active' protection/screening processes that run anytime your browser is open for instance (i.e.: something intregrated into the browser as an add-on, etc). Most of the time, multiple 'stand-alone' (or on-line) scanners run outside of the OS/browser will not hurt the OS.

Just sayin' ...

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