What is MsMpEng.exe? Is MsMpEng.exe spyware or a virus?

How to fix MsMpEng.exe related problems?
1. Run Security Task Manager to check your MsMpEng process
2. Run Windows Repair Tool to repair MsMpEng.exe related Windows Errors
3. Run MalwareBytes to remove persistent malware

Process name: Service Executable or Antimalware Service Executable or AntiMalware Service Executable or Microsoft Antimalware

Product: Windows Defender or Microsoft Malware Protection or Microsoft Security Essentials or Microsoft Windows Operating System or Microsoft Antimalware Service or Windows Defender Service

Support: Help link [1][2]   Update link [1][2]   Uninstall tool  

Company: Microsoft (microsoft.com)

File: MsMpEng.exe


MsMpEng.exe is a core process of Windows Defender, which is Microsoft's antispyware utility. It scans downloaded files for spyware; if any suspicious items are found, it can quarantine or remove them. It also takes steps to actively prevent spyware infections by searching the system for known worms and trojan programs. Terminating the process will compromise system security; disable Windows Defender within Windows if using a different antispyware product.http://www.neuber.com/taskmanager/process/msmpeng.exe.html 

If you want a detailed security rating about your MsMpEng.exe (and all other running background processes) read the following user opinions, and download the free trial version of Security Task Manager.

Note: Any malware can be named anything - so you should check where the files of the running processes are located on your disk. If a "non-Microsoft" .exe file is located in the C:\Windows or C:\Windows\System32 folder, then there is a high risk for a virus, spyware, trojan or worm infection! Check it out!


Click to Run a Free Scan for MsMpEng.exe related errors


Users Opinions

Average user rating of MsMpEng.exe: based on 168 votes. Read also the 153 reviews.

  • 2418 users ask for this file. 99 users rated it as not dangerous. 11 users rated it as not so dangerous. 23 users rated it as neutral. 12 users rated it as little bit dangerous. 23 users rated it as dangerous. 14 users didn't rate it ("don't know").

All comments about MsMpEng.exe:
Safe, STM should update Tom
MS spyware program, not dangerous, but useless Terry
Windows defender file Anthony Colley
Windows Defender
It is microsoft windows defender, free to download to Mike
Windows Defender  See also: Link Jeremy
Safe. It is a resource hog when running it full scan but I usually turn the priority to idle when i notice it. Neo
Windows Defender/Windows One Care  See also: Link Bill
This is safe. but more resource consuming
Windows Defender....if you installed it you should know.....hopefully you do....by microsoft!
safe -use windows defender to check my system denise
its a windows defender process
Windows Defender, eats CPU usage sometimes Nicko
process to do with MS Defender  See also: Link Peter
Belongs to "Microsoft Defender" (AntiSpyware-Program) Beta 2 Rubberduck
Windows Defender (anti spyware) scanning your PC for threats. charlie
this file is an update-manager. After download Microsoft wants you to restart to make updates work. When you restart problem is solved. G.A. Taatgen jr.
is a process belonging to Microsoft Windows Defender Antispyware. Manufacturer: Microsoft Corp. http://www.microsoft.com/athome/security
There are way better anti spys around. AVGAS and SpyBotS&D. in its original form (Giant) Defender was good, now it ignores too much crap from MS advertising friends. My PC runs better without it. Bevan Miller
As its a windows Addin product for Windows security, than it proovs that we do not have any threat from it. But negative comment is when this file starts its process it eats 50 % or more of your system speed, which alternatly slow downs other applications running on your computer, due to which your system performence comes down. Geetesh
It is part of Windows Defender. You can remove it through add/remove programs or other removal tools. It is difficult to set the scan times as it appears to be random on my machine even though I set it for 2 am. F. Frye
Its the microsoft programs "windows Defender beta 2". It goes to very high levels if it doing an auto scheduled scan. David V Hacker
Windows Defender Process
part of winxp defender, eats a lot of cpu but only lasts for a couple of mins Beaglex2
Part of the Microsoft Windows Defender anti-spyware service Marc J. Miller
MS defender(antispyware beta) absolute cpu hog. D_B_D
Executable is in "C:\Prog ... \Windows Defender\" pszczepa
Part of Ms Defender Beta. Hogs memory
resource hog, it causes the computer to stop and then you cannot use it for some time and it also causes continual slowdowns on the computer useless beta from microsoft. Jim Robinson
It is the process for Windows Defender. Tends to greatly bog down system resources. Can use up to 99% of your CPU, even when not running. Easy fix is to uninstall Windows Defender.
Resident part of Microsoft Defender  See also: Link Hogar
Not a security risk, but can turn itself effectively into malware, eating CPU resources. Ifrit
Not Dangerous but consumes more resources. we can try turning off Indexing Service to reduce the consumption. vensgal
Windows Defender, takes a lot of resources for little work
Microsoft's Windows OneCare (antivirus and anti spyware) Steve
Windows Defender Paperoga
CPU hogging process
Will peg cpu, and hog I/O, may install on servers, causing difficult to find bottlenecks. CER
Windows Defender is just doing a timed system scan if MsMpEng.exe is taking alot of computer prosessing. Ken
As said, it's Windows Defender... On my machine the I/O is what realy stood out to me... This program had read and written more than all other programs combined... CJ
Windows Defender Johannes
Some people find it really hogs the cpu almost to the point of the computer becoming unusable. Of course that's when it scans. But it isn't dangerous.
Windows def.file Pinda!
It's a process for Windows Defender Spyware program. Safe to end this process. Gooseman
Windows Defender
windows defender H55
Windows Defender. On one machine of mine it eats up to 30% CPU time Calbo
MS Defender component, do not end while running. If you want, uninstall Defender to solve the problem ko
Windows did not do a very good job with this one. Disabled my firewall several times Tem
Windows Defender process  See also: Link Jim
Is Microsoft. Also is known to consume 100% CPU at times. Chuck
spyware, Bob
part of windwos defender M
but it hogs up 50% of my Core Duo Ben
hotbar 4.8.4.0
Not dangerous but annying: it uses 100% of CPU for a few minutes at Windows startup .Windows Defender can be safely deleted. Use Adaware and Spybot instead.  See also: Link Henry.
best security for geniun xp frankie
its part of the Live One Care program Abdullah
Slows system down considerably Sir Sensible
File belonging to Microsoft Windows Defender (previously made by Giant). Not dangerous -- if this file exists and you don't have Windows Defender, then there is a problem :)  See also: Link C.M.
while typing only this reaction is it's using 70 - 97 procent of cpu (..) Ron
window live masenger
2.6 celeron 512ram- this file takes up 65%~ cpu power- reason unkown ger
MsMpEng.exe is the Windows Defender Process. It likes to hog memory...but I don't trust anything other than Microsoft's Products. Anon
Used with windows live one care, only eats up cpu when it is being used, barely uses any cpu when its not being used Nathan
CPU/Disk access heavy during PC startup, Slows things down. WEmmons
task message ("not responding") also ending program (end now and cancel) Larry D.Luckert
so well ending programrelated by end now /cancel also related by task manger to it is ("not responding ") requested to be evicted do not reput it that back ("self defender") Larry D.Luckert
Before I download defender, my PC worked perfectly. With defender, tit runs extremely slow. I ever used to spyware doctor which also ate too much CPU. So I finally ininstalled this anti spyware program. I think these antivirus softwarer developer exaggerate their functtions. Acutally what they do is very lmited. I doubt defender. Richard
Add the Microsoft Windows Onecare\antivirus folder to the exclusions of OneCare Virus and Spyware settings. Passasw
Another Resource Hog, but for the protection may be acceptable RaeJie
started with windows one care. slowed down computer so it is unusable
microsoft defender, safe, but eat up lot of memory some times Michael YKS
Виндовс Дефендер Adolf
uninstalled lavasoft ad-ware,seems, ok now s white
processor hog, uses 83/100% processor Jim Themel
Can slow your system down if you've got a crap system... I've never had any problems with either Defender or OneCare apart from on an old Compaq laptop, which refuses to keep either product stable for more than 5 minutes without the service stopping itself for no reason at all. I've yet to track down precisely why this is happening. Either way, if you are having problems with this file, remove either Defender or OneCare and use an alternative product. Your system will remain unharmed. Jonathan Thorpe
This is a Windows Defender process. Since the HD use lite flickers, I think Defender is running a malware SCAN. Depending on your drives it may take up to an hour or so. After that the CPU usage goes away and so does the HD lite. Only happens on start up once in a while. I will check Defender settings for scheduled scans. Clicked on Windows Defender in "all programs" and it was in the middle of a Full System Scan. After scan showed completed HD lite off and CPU usage back to normal. In Defender, under TOOLS, then OPTIONs (IN XP SP3) the default seems to be a daily full system scan. Uncheck automatic scans, and updates before scans, if you want. Then run updates and scans manually. Doug
It is part of the Win Defender package and possibly other software as well, such as the OneCare Package. It occupies 90% CPU when running. It runs when my antivirus is scanning lots of files. My antivirus also uses 90% CPU! My solution is to delete Defender. Doom
Windows Defender executable. Tries to find latest updates which occur about 2x a day. If Automatic Updates is turned on, Defender "calls home" frequently looking for updates and hogs CPU. Turn off Automatic Updates and manually check for ALL updates regularly. MsMpEng will still hog CPU at startup but for seconds, not minutes. Will also spring to life at questionable websites. But CPU usage will be minimized. I manually update Defender once in A.M. and once in P.M. Go to Windows Defender website, click on latest updates. Ben
It gorges on memory and causes Windows Media Player to skip. Has also been known to stubbornly refuse to shut down. Right royal pain in the arse.
It uses too much memory & CPU - computer running all the time
It is Windows Defender file. You can reinstall application to fix the MsMpEng error. Avin Tokade
Now a pest hogging Cpu soon after macine start. And, furthermore, does not provide sufficent details when it triggers a warning, has reached uselessness. Lionel
this is part of Microsoft Security Essentials. If you have Microsoft Security Essentials installed, go to Program Files and check it out. Jim Cockrill
Windows Defender and Windows Live One Care both use this scanning engine. It is not likely that the exe file has been corrupted, since it is a part of the anti-malware system. It can, however, be annoying as you-know-what, because of its seemingly random run times. This is because there are numerous events that trigger it (e.g. updating feeds, polling e-mail servers, attaching a new USB storage device) - not just during a scheduled scan. Defender comes integrated in Windows Vista. If you have another anti-virus program, Defender can and should be turned off.  See also: Link awgie-dawgie
waste of (CPU) time
CPU freezer. it likes to slow down your computer spontaneously. writtern by two-left-hands programmer. BobSwat
Windows Defender process; it likes to scan files when you open them. If it does this at the wrong time for a video file or the like, it can crash your computer. C'mon, there's a reason you find so many people mistaking it for malware. Lance
Runs Windows Defender, MSE. If you have remenants of AVG, Avast, or other AV programs, as I did, they may not be fully uninstalled. Causes MsMpEng,exe to run in and endless loop. I downloaded removal tools from AVG and Avast! and ran them. No more problems. MsMpEng.exe uses very little cpu time, except when running scan, which I do now at late night.(I now use MSE) Richard
can disable in control panel\administrative tools\services vgp
This is part of Microsoft Security Essentials. It slows down the system when it checks for updates.  See also: Link Danny
Windows defender file. Consumes a lot of cpu when scanning, but then cpu returns to normal after scan. Have noticed that it chews at the cpu usage after I maually update, does a quick scan after the update which takes only a minute or two. I have disabled it on startup and only use when scanning or updating defenitions.
On XP, it's also part of MS Security Essentials. David
to delete look for Microsoft Security as the program name Chrystin Pleasants
It's also associated with Windows security Essentials, which is tarted up and glorified Windows defender Supah D
will slow down netbook. Daniel
Microsoft Security Essentials, major resource hog. Should you other antivirus and uninstall this. Alexxoo
Related to Microsoft Securty Essentials
This is part of Microsoft Security Essentials. I do not have Windows Defender on my computer. I found the file in the MSE folder. Gale
do not let the Windows Defender scan the folder to which it is installed, this will slow down the scan to a crawl. Mine was installed to the following folder: C:\Program Files\Windows Defender. You can exlude scanning this folder at the Options setup. Karin Ulloa
It uses up more than half of my CPU at any given time, sometimes op to 90%!I can't even destall it. There's no point in a safe computer if its slow.
poor quality scanner and resource hog archwaygunner
Microsoft Security Essentials MSE  See also: Link no
MS Security Essencials - Nice soft but not good to old computers... it needs good memory and processor Roberto Novakosky
Eats most of my CPU memory and access, freezes my computer!
Slows computer boot & running. Decided to dump. Don
part of Microsoft Security Essentials on my XP system. LtfJ
A Microsoft process installed by Security Essentials. Causes periodic (1X/2sec) distortion when playing an audio file. Stopping this process stops the distortion. Obviously a poorly designed process by MS. Sigh.
I have it active right now and my total CPU usage is about 9%. It removed a scareware product "Security Defender" from my son's laptop after Spybot and Malwarebytes couldn't find it. Eric
Eats up to 70% of CPU almost all the time even if nothing is being downloaded! Never reported about the malware. The question - what does it do?! Andrei
Microsoft Security Essentials great because it is free! Reg
Its a virus that key-logs your every move. It steals your password to everything, but it's not dangerous. T.G.I.F.
keylogger from microsoft (limit cfg no original licsence) headshot
Part of microsoft security essentials. Loading this page in firefox takes more cpu then msmpeng.exe idle or when MS Security is doing a quick scanning! Full scans will take up memory but every security software does if its doing its job, remember its going through just about everything on your computer. This is on 3.5 GB ram, single core 2.11 GHz AMD Athlon XP 2800+ introduced in Oct of 2002 that's almost 10 YEARS OLD. Its part of security software and is only dangerous to impatient people that still use windows defender on auto scan, their fault lol. However, I would recommend that you install a new antivirus before you delete your current one because if it's bogging down your computer it's because its trying to keep you safe from all the bad things your looking at on the web :). Always do full scans manually and when you don't need a huge part of your cpu. aka. downloading stuff or gaming. Austin
It is a keylogger if asks to run at startup by unknown publisher John
MSSE, horrible detection rates make this worthless. All it does is eat your CPU and RAM. Use something that actually blocks threats and is not shitty.  See also: Link Bai
no biggie.. runs in background lil bit of defense fritz
acualy dose catch stuff if you use the internet hevily like myself. i have a intel i7 wit 16gb ram so i don't notice a slow down ZMZ
It's a security application on Windows (Detail: Antimalware Service Executable, Microsoft Trusted APP) that uses a lot of CPU when browsing first time folders.  See also: Link Aoryu
It slowed my old cpu to a crawl
Can cause CUP utilization issues. Basically forefront issue. Anonymous
Microsoft Security Essentials, good stuff - and free! mfalkvidd
safe but hogs alot of cpu sometimes phanalax
It definitely is CPU hog! It's not my puter, or I'd dump it! Elise
Found it under Administrative Tools Services in a long list but luckily it is alphabetical. It is is called Microsoft Antimalware Service and can be stopped if you want to do that and it can be restarted later if you find you need it. Robert
i didnt installed windows defender but microsoft security essentials and now this file is running in background processes Ali Zulqarnain
eating up my processor power and find it most irritating douglas johnson
I installed Microsoft Security Essentials at which time Windows Defender was disabled so I was informed. Now I see MsMpEng.exe which is in fact the executable for Windows Defender running sneakily in the background hogging my CPU. Stan
Microsoft Security Essentials if installed... If not, it's Windows Defender. I tried to end its process and MSS Essentials popped up a Window that it cannot scan because the process was ended. I clicked the button that said "Start Now" and it was ok... It's good stuff! You can go to the settings of MSSE and tell it not to use much CPU. I have it limited to 50% but since I have 3 cores I have nothing to worry about. Chriskalos
It's a PITA on startup, consuming a lot of CPU time for an extended period of time. I tend to stop it at once in Taskmanager. Restarts by itself after a short time and then just running without consuming too much CPU time. On one computer MSSE stops for a few minutes with a popup warning, on the other computer MSSE just continues running.
Windows Defender, totally safe Lord Voldemort
Used for Microsoft antivirus
Made my computer run about 10 times slower after installing. Same to my friend's computer. We are both uninstalling and replacing it. Shawn
Windows Defender Service, may not be needed if running Microsoft Security Essentials, which is supposed to disable it according to this:  See also: Link Bilbo Baggins
This is the working party of MS's Defender. You can set it to how much of your Proc's time to use, however, note that it runs on one thread only, at least on Windows XP-3 so that it will use 100% of your Proc if you set it for '50'. It is very easy to program how much, what to scan or not, how often and when. If you suspect malware, first update the definitions even if they are only 4 days old, then run a quick scan. If that doesn't find anything and something still seems wrong with your PC, depending on the suspectected severity, you can immediately do a Full scan and go take a shower or make lunch, or wait 'till bedtime and let it do a full scan for as long as it needs. It will quarentine any malware it finds, and in the morning you can do what it recommends to do; ie. remove it. This got two severe viri that I got when I was suckered into while looking at photos of Selena. The first full scan didn't get them. I updated the definitions that were 4-5 days old, ran a full scan again and successfully unfroze the PC. Boss Oldman.
Horrible. Eats up CPU and Memory usage. Sid
Microsoft Security Essential and eating periodically RAM memory up to 90% and everything stopped and freezing computer to work for 10-20 minutes depends of what is hungry (Takes you your time). Uninstall it. More FREE Time
in safe mode, this rating is high
Eats 99% of my RAM and I have 10GB ram. I'm uninstalling MSE Yurippe
It is more dangerous that more of the virus that it found, it slow down your computer tooooo muchhhhhh. bob70
too much CPU usage.. :/
Part of Forefront Endpoint Protection. VictorMR
Eats up a lot of CPU, can even crash computer at times. Running on Win 7 but given enough time, it'll refresh itself. TheDragon
Part of Windows Defender Not dangerous, but it hogs memory and CPU threads Chernobyl
Windows Defender!!!!
more CPU usage thane any security software . Abu Joloud
this will take up all you cpu making your computer useless find a way to get rid of it because it will make your pc unusable Joe
it started bogging down the cpu after i opened a file that was malicious (im guessing) i deleted the file and cleared the recycle bin and msmpeng went back to normal. so it would seem that whatever your doing when msmpeng starts to bog you comp down is the cause, not msmpeng itself. then again i only know the basics of computers so i might be wrong. hope-it-helps
eats my cpu like its candy, avoid this anti virus program at all costs,poor me victim
This is the built in Windows Defender by Microsoft or the Microsoft Security Essentials antivirus. It is safe. Ivan
Constant CPU hog. Not worth what little (very little) it does. Other
In my case I would NOT call it dangerous but it is harmful in the respect that it consumes way too much of the computers resources like cpu time & memory. webatch

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Is MsMpEng.exe spyware or a virus, trojans, adware or worm? Is there a known MsMpEng.exe error?


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MsMpEng.exe [all processes]