MBR:Cidox-E [rtk] how did avast not detect this?

I’m sorta new to avast forums, I’m just here for help. So yesterday, Halloween, I was just opening up garry’s mod when suddenly avast said it detected malware in explorer.exe, and then my PC just bluescreened. upon restarting, my pc started lagging terribly. avast didn’t find anything until i did i system restore. It said that a rootkit called MBR:Cidox-E [rtk] was on my computer. It removed it… well i guess it did, and it did a boot time scan. after that, i went back on my pc, and everything stopped lagging after that. it didn’t say it detected a rootkit or anything, so I’m gonna guess it’s gone. what im wondering is, how didn’t avast see this when the virus was first installed? like, why didn’t it give me a warning or anything? I have no clue where I got the virus from, and the fact that avast didn’t detect it at first is even weirder.

-No security program have 100% detection or zero false positives
-avast may have gotten signature for it after you got it
-it can be a false positive

what was the name and location of the file … full file path

if you want a check …

Instructions https://forum.avast.com/index.php?topic=53253.0
Attach Malwarebytes and Farbar Recovery Scan Tool and aswMBR logs … 4 logs total

See below the box you write in … Attachments and other options

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