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sc0rpi0
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  • 3 weeks later...
Theoretically if you encrypt the file strong enough it wouldn't be found by a AV,though it would take longer for the file to run,the stronger the encryptions is the longer it takes to decode it...

But won't it stop the program from running until it CAN decode it?

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Well,theoretically speaking,we are talking about somewhere between some milliseconds and maybe a few seconds,depending on the encryption used...

But won't it stop the program from running until it CAN decode it?

I'm not exactly sure i understand your question...

The program would be run like any normal payload,with the difference that it decrypts itself into memory at some point...which would be pretty much the only point it would be detectable...

The AV wouldn't be able to detect it as a known 'virus',except of course,if it is a bad encryption,or it somehow behaves stupidly...

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One of two things will happen:

1. When the program is decrypted the AV grabs it

or

2. The AV will detect the embedded code used to decrypt the executable (because the .exe will not magically decrypt itself there needs to be code there to do it) and probably flag that as  a virus / suspicious

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One of two things will happen:

1. When the program is decrypted the AV grabs it

or

2. The AV will detect the embedded code used to decrypt the executable (because the .exe will not magically decrypt itself there needs to be code there to do it) and probably flag that as  a virus / suspicious

V'cent, sablefoxx is right. The executable will be decrypted into memory at _some_ point, and the AV will grab it.

The only other solutions are making a rootkit or recompiling source with different settings/addded dummy code.

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One of two things will happen:

1. When the program is decrypted the AV grabs it

or

2. The AV will detect the embedded code used to decrypt the executable (because the .exe will not magically decrypt itself there needs to be code there to do it) and probably flag that as  a virus / suspicious

V'cent, sablefoxx is right. The executable will be decrypted into memory at _some_ point, and the AV will grab it.

The only other solutions are making a rootkit or recompiling source with different settings/addded dummy code.

Really n00b question:

How would I go about making a rootkit?

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But won't it stop the program from running until it CAN decode it?

I'm not exactly sure i understand your question...

The program would be run like any normal payload,with the difference that it decrypts itself into memory at some point...which would be pretty much the only point it would be detectable...

The AV wouldn't be able to detect it as a known 'virus',except of course,if it is a bad encryption,or it somehow behaves stupidly...

Well,if we look at my post here,you see the same conclusions from sablefoxx ,though he stated it clearer...the program will be catched in memory or in the decrypter embedded in the file,though there are workarounds for both...BTW Sc0rpi0 i would NOT recommend creating a rootkit though,since it makes the targeted system VERY unstable and mis configures it pretty bad too,that is,if you aren't an expert on what you are doing...

¨Whatever you choose,good luck  :-)

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But won't it stop the program from running until it CAN decode it?

I'm not exactly sure i understand your question...

The program would be run like any normal payload,with the difference that it decrypts itself into memory at some point...which would be pretty much the only point it would be detectable...

The AV wouldn't be able to detect it as a known 'virus',except of course,if it is a bad encryption,or it somehow behaves stupidly...

Well,if we look at my post here,you see the same conclusions from sablefoxx ,though he stated it clearer...the program will be catched in memory or in the decrypter embedded in the file,though there are workarounds for both...BTW Sc0rpi0 i would NOT recommend creating a rootkit though,since it makes the targeted system VERY unstable and mis configures it pretty bad too,that is,if you aren't an expert on what you are doing...

¨Whatever you choose,good luck  :-)

My question was whether the program [for example: netpass] if encrypted would have enough time to perform its function of extracting passwords

before the AV caught it. I'm assuming the answer is yes, but just double checking. Thanks for your help.

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Depending on how good the AV does it job on checking memory constantly,your little payload would probably work pretty well,until some AV company finds out about it... :-P

So,yes theoretically speaking it would work...safest method to find out is still a virtual server and testing it  :)

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Any modern AV monitors _constantly_ for the opening of files - vbs, doc, exe and many more file types - and _before_ they are opened, they are scanned. After they are opened, memory is scanned every x milliseconds to check if any process created a malicious thread or contains a malicious file.

So, atm where the AV gets to know the .exe in its definition file, the only thing you can do is to obscurize it with UPX.

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