Why is MSSE's MsMpEng.exe using insanely high amounts of memory?

I'm running MSSE v1.0.1961 with the latest definition file but tonight while I was browing I received a low memory warning from Windows despite having 6 GB of system RAM and 3 GB worth of pagefiles spread across two HDDs. I'm running Windows 7 Home Premium x64 on a 128 GB Crucial M225 SSD and Superfetch is disabled so Windows only uses around 1.5 GB of memory normally.

When I checked Task Manager I saw that MsMpEng.exe, the main MSSE file, was using over 5 GB of RAM. I rebooted my PC, which took about 10 minutes due to the heavy RAM and pagefile usage but the problem still crops up although I've noticed it was around 1.5 GB this time. If left though the real-time scanner eventually hits 3+ GB so I had no option but to disable MSSE's scanner. If I kill the real-time scanner then the memory usuage drops back down to the normal 70 MB or so.

The only things I've installed on my PC today were three or four updates from Windows Update this morning. What on earth is causing this excessively high RAM usage... a bug in the latest definition table or some incompatibility with one of the recent Windows updates ?

My PC specs are:

Intel Core i7-920 @ 3.36 GHz, ASUS P6T Deluxe motherboard (v2101 BIOS), 6 GB DDR3 1,600 MHz RAM, 2 x Sapphire ATI Radeon HD 5870 Vapor-X (CrossFireX) graphics, Creative Sound Blaster X-Fi XtremeGamer sound, 128 GB Crucial M225 SSD (boot drive), 2 TB 7,200 rpm SATAII HDDs (storage), LG DVD-Rewriter, Windows 7 Home Premium (x64).

I've been using MSSE for months since it's official release last year with no issues until recently, definitely yesterday but possibly my issues go back a few weeks to when I installed my first HD 5870 card as I received some Windows warnings about graphics memory being low and to switch to Aero, always after exiting a game though, something that is ridiculous on my system when you consider than my cards score 7.8 in both the graphics test on Windows Experience Index and that I have graphics with 1 GB of memory each and system memory of 6 GB plus 3 GB of virtual memory!

UPDATE: I was just playing Metro 2033 this morning to see how much memory it used via Task Manager when I noticed that MsMpEng.exe was again using 1.5 GB. If I turn off the real-time scanner then the memory usage drops down to 80 MB (it's currently at 95 MB). As such I've now decided to disable the real-time scanner until I can isolate what is causing this 'bug' because I've no doubt now that this is what has been causing the low memory warnings I've been having for the past few weeks while running games.

There's no way any anti-virus/anti-malware program should be using more than a few hundred MB nevermind 1.5 to 5 GB as it has been doing on my system. If I can't solve this then I'll have to consider using another program. I'm really disappointed to be honest because I've been using MSSE for a quite a while now and haven't had any issues with it at all until recently.
Question Info

Last updated June 22, 2018 Views 37,509 Applies to:

I may be tempting fate here because MSSE may be just behaving the way it is due to a random bug but I've just scanned both the crack PES2010.exe and original BFBC2Game.exe files and MsMpEng.exe did you use any more than 70 MB taking just a few seconds each to scan them. Now I checked to make sure that the *.EXE exclusion had been deleted and that the folder pathnames are not excluded either. They weren't.

So has this issue been fixed with the latest Definition table (1.81.780.0)? It would be nice to hear some confirmation from Microsoft I think that it has because someone at their end is supposed to be ringing me on Monday to try to help me fix the issue. It would be a waste of theirs and my time if it has.

Version details for MSSE are:

Microsoft Security Essentials Version:  1.0.1961.0
Antimalware Client Version: 2.1.6519.0
Engine Version: 1.1.5703.0
Antivirus definitions: 1.81.780.0
Antispyware definitions: 1.81.780.0

If anyone else thinks it may be fixed then try scanning the files I mentioned and see if MSSE reports no malicious items on 1 item (whilst right-clicking on the executable and selecting Scan with Microsoft Security Essentials) as it did for me. It should be almost instant and you shouldn't see any abnormal memory usage.

Did this solve your problem?

Sorry this didn't help.