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Malware Analysis
[Video] 3CX SmoothOperator C2 extraction
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<blockquote data-quote="struppigel" data-source="post: 1034547" data-attributes="member: 86910"><p>[MEDIA=youtube]_jsgCRNcf1o[/MEDIA]</p><p></p><p>To obtain more IoCs we analyse the second stage DLL that we decrypted in the first 3CX video. Then we create a CyberChef recipie that extracts and decrypts the C2 URLs. Afterwards we convert this recipie to a binary refinery snippet which allows us to do the same from the command line for all of the icons.</p><p></p><p>Samples:</p><p>Icons: <a href="https://bazaar.abuse.ch/sample/2b5758f388027c53af132a2c7b28b3448b9869a81a5ce134c78330a3c31181f5/" target="_blank">MalwareBazaar | Browse Checking your browser</a></p><p>3CXDesktopApp.msi: <a href="https://tria.ge/230330-3nzfjshc2s" target="_blank">Triage | Malware sandboxing report by Hatching Triage</a></p><p>ffmpeg: <a href="https://bazaar.abuse.ch/sample/7986bbaee8940da11ce089383521ab420c443ab7b15ed42aed91fd31ce833896" target="_blank">MalwareBazaar | Browse Checking your browser</a></p><p>d3dcompiler_47.dll: <a href="https://bazaar.abuse.ch/sample/11be1803e2e307b647a8a7e02d128335c448ff741bf06bf52b332e0bbf423b03" target="_blank">MalwareBazaar | Browse Checking your browser</a></p><p></p><p>Infection chain graphic: [MEDIA=twitter]1641668394155151366[/MEDIA]</p><p></p><p>Binary Refinery: <a href="https://github.com/binref/refinery" target="_blank">GitHub - binref/refinery: High Octane Triage Analysis</a></p><p></p><p>Volexity article: <a href="https://www.volexity.com/blog/2023/03/30/3cx-supply-chain-compromise-leads-to-iconic-incident/" target="_blank">3CX Supply Chain Compromise Leads to ICONIC Incident | Volexity</a></p><p>Volexity Python icon decrypter: <a href="https://github.com/volexity/threat-intel/blob/main/2023/2023-03-30%203CX/attachments/decrypt_ico.py" target="_blank">threat-intel/decrypt_ico.py at main · volexity/threat-intel</a></p><p></p><p>CyberChef recipie: <a href="https://gchq.github.io/CyberChef/#recipe=Regular_expression('User%20defined','%5C%5C$(%5BA-Za-z0-9%2B%3D/%5D*)$',true,false,false,false,false,false,'List%20capture%20groups')From_Base64('A-Za-z0-9%2B/%3D',true,false)To_Hex('None',0)Drop_bytes(0,8,false)Register('(%5B%5C%5Cs%5C%5CS%5D%7B32%7D)',true,false,false)Drop_bytes(0,32,false)AES_Decrypt(%7B'option':'Hex','string':'21%20A1%20AC%20E1%20E6%2063%20BA%2045%2086%204D%20F4%2057%20B2%2009%2018%201E%20BD%2090%2010%201B%204A%2051%2028%2040%2038%207C%20D2%2010%20E5%208F%20A3%20F1'%7D,%7B'option':'Hex','string':'3B%208A%2008%20ED%200F%209E%2008%20CA%2057%2021%2009%20EF'%7D,'GCM','Hex','Raw',%7B'option':'Hex','string':'$R0'%7D,%7B'option':'Hex','string':''%7D)Remove_null_bytes()" target="_blank">CyberChef</a></p><p></p><p>00:00 Intro</p><p>00:30 Preliminary analysis</p><p>03:50 Extracting the DLL from shellcode</p><p>04:43 Finding the icon decryption function</p><p>08:11 Analysing the decryption function</p><p>22:10 Recap, tl;dr current goal</p><p>24:37 Obtaining Key and IV with debugging</p><p>29:56 CyberChef recipie creation</p><p>38:40 CMD decrypter creation with Binary Refinery</p><p>44:00 Why I used IDA Free this time</p></blockquote><p></p>
[QUOTE="struppigel, post: 1034547, member: 86910"] [MEDIA=youtube]_jsgCRNcf1o[/MEDIA] To obtain more IoCs we analyse the second stage DLL that we decrypted in the first 3CX video. Then we create a CyberChef recipie that extracts and decrypts the C2 URLs. Afterwards we convert this recipie to a binary refinery snippet which allows us to do the same from the command line for all of the icons. Samples: Icons: [URL="https://bazaar.abuse.ch/sample/2b5758f388027c53af132a2c7b28b3448b9869a81a5ce134c78330a3c31181f5/"]MalwareBazaar | Browse Checking your browser[/URL] 3CXDesktopApp.msi: [URL="https://tria.ge/230330-3nzfjshc2s"]Triage | Malware sandboxing report by Hatching Triage[/URL] ffmpeg: [URL="https://bazaar.abuse.ch/sample/7986bbaee8940da11ce089383521ab420c443ab7b15ed42aed91fd31ce833896"]MalwareBazaar | Browse Checking your browser[/URL] d3dcompiler_47.dll: [URL="https://bazaar.abuse.ch/sample/11be1803e2e307b647a8a7e02d128335c448ff741bf06bf52b332e0bbf423b03"]MalwareBazaar | Browse Checking your browser[/URL] Infection chain graphic: [MEDIA=twitter]1641668394155151366[/MEDIA] Binary Refinery: [URL="https://github.com/binref/refinery"]GitHub - binref/refinery: High Octane Triage Analysis[/URL] Volexity article: [URL="https://www.volexity.com/blog/2023/03/30/3cx-supply-chain-compromise-leads-to-iconic-incident/"]3CX Supply Chain Compromise Leads to ICONIC Incident | Volexity[/URL] Volexity Python icon decrypter: [URL="https://github.com/volexity/threat-intel/blob/main/2023/2023-03-30%203CX/attachments/decrypt_ico.py"]threat-intel/decrypt_ico.py at main · volexity/threat-intel[/URL] CyberChef recipie: [URL="https://gchq.github.io/CyberChef/#recipe=Regular_expression('User%20defined','%5C%5C$(%5BA-Za-z0-9%2B%3D/%5D*)$',true,false,false,false,false,false,'List%20capture%20groups')From_Base64('A-Za-z0-9%2B/%3D',true,false)To_Hex('None',0)Drop_bytes(0,8,false)Register('(%5B%5C%5Cs%5C%5CS%5D%7B32%7D)',true,false,false)Drop_bytes(0,32,false)AES_Decrypt(%7B'option':'Hex','string':'21%20A1%20AC%20E1%20E6%2063%20BA%2045%2086%204D%20F4%2057%20B2%2009%2018%201E%20BD%2090%2010%201B%204A%2051%2028%2040%2038%207C%20D2%2010%20E5%208F%20A3%20F1'%7D,%7B'option':'Hex','string':'3B%208A%2008%20ED%200F%209E%2008%20CA%2057%2021%2009%20EF'%7D,'GCM','Hex','Raw',%7B'option':'Hex','string':'$R0'%7D,%7B'option':'Hex','string':''%7D)Remove_null_bytes()"]CyberChef[/URL] 00:00 Intro 00:30 Preliminary analysis 03:50 Extracting the DLL from shellcode 04:43 Finding the icon decryption function 08:11 Analysing the decryption function 22:10 Recap, tl;dr current goal 24:37 Obtaining Key and IV with debugging 29:56 CyberChef recipie creation 38:40 CMD decrypter creation with Binary Refinery 44:00 Why I used IDA Free this time [/QUOTE]
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