Hackers Attacking Windows IIS Server to Upload Web Shells

Windows IIS Servers often host critical web applications and services that provide a gateway to sensitive data and systems due to which hackers attack Windows IIS servers.

A South Korean medical establishment’s Windows IIS server with a Picture Archiving and Communication System (PACS) has been attacked, as identified by AhnLab Security Intelligence Center (ASEC), which resulted in CoinMiner infections.

There are several suspicions of web shell uploads indicating possible PACS vulnerabilities or wrongly configured safety settings.

The attacks were two different situations just days apart, probably organized by Chinese hackers who used various tools like Cpolar and RingQ, complete with Chinese annotations.

This event is an example of the continuous targeting of exposed web servers in Korea but specifically directed towards China-speaking groups emphasizing the importance of having secure measures for such critical systems like PACS in hospitals.

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Hackers Attacking Windows IIS Server

Firstly, an attack was launched against a Korean medical institute’s web server via upload of Chopper and Behinder web shells, followed by system reconnaissance.

For privilege escalation, BadPotato was deployed by the threat actor, while Cpolar was used for remote access. A CoinMiner came in through a “1.cab” file that contained batch script, task scheduler XML, and downloader.

Finally, some Chinese-speaking attackers had chosen the above tools and also made annotations on the scripts. 

They included several additional web shells (ASPXspy, Caidao), privilege escalation tools (PrintNotifyPotato, IIS LPE, GodPotato), port forwarding tools (Lcx, Frpc), as well as user account creation malware.

Consequently, this all-inclusive toolkit provided continuous accessibility to the compromised server, which enabled governing it, and assisted in cryptocurrency mining.

Days later, the second attack was launched on the web server of a Korean medical institution. 

The attacker also used Certutil to download additional malware and installed more privilege escalation tools such as GodPotato, PrintNotifyPotato, and CVE-2021-1732 exploit which were among others network exploration tools deployed like fscan, remote shell, and Netcat.

EarthWorm served as a proxy tool while Ladon is a multi-functional Chinese-built tool that handles different steps in an attack process.

Besides that, evidence suggests that the threat actor may be a Chinese speaker, who used RingQ to encrypt and execute malware in memory to bypass file-based detection.

Consequently, they finely crafted an ASPX downloader as XMRig CoinMiner which had some of the most advanced evasion techniques or even focused on crypto mining.

Recommendations

Here below we have mentioned all the recommendations that the security analysts provide to prevent such attacks:-

• Administrators should address file upload vulnerabilities.
• Implement regular password changes.
• Access controls to mitigate lateral movement risks.
• Keep antivirus software updated.

IOCs

MD5

First Attack Case:-

– 67af0bc97b3ea18025a88a0b0201c18d: WebShell – woanware (1.aspx)

– f6591c1ab7f7b782c386af1b6c2c0e9b: WebShell – woanware (2.aspx)

– 986c8c6ee6f6a9d12a54cf84ad9b853a: WebShell – Chopper (2a.aspx)

– 2183043b19f4707f987d874ce44389e3: WebShell – Behinder (32.aspx)

– 77d507d30a155cf315f839db3bf507f7: WebShell – Behinder (1234a.aspx)

– 8d52407e143823a867c6c8330cdcb91a: WebShell – Behinder (1235a.aspx)

– 73cdd1be414dec81c6e42b83f0d04f20: WebShell – Behinder (12345a.aspx)

– 7e9f28cedfa8b012ab8646ac341a841c: BadPotato (bad1231.exe)

– 8cf601c06370612010f438fa8faa8aa7: Cpolar (cpolar.exe)

– e2753e9bc7e5880a365f035cdc5f6e77: Runner (1.bat)

– 205e6247f5a0dce8a55910354c816a61: ScheduleTask (1.xml)

– e13adb67739f4b485544ed99bc29f618: NSSM (service.exe)

– f3bdcd409063a42479dbb162dc7f5d21: CoinMiner downloader (svchost.exe)

– fce1b5ffcaefd1dcb130f4e11cdb488d: CoinMiner downloader (sihost.exe)

– a66338d9ba331efa4918e2d6397b17fe: CoinMiner (SecurityHealthServices.exe)

– 40dc8989d4b2e3db0a9e98ef7082b0d9: WebShell – ASPXspy (aspx.txt)

– b69eb0155df920514d4ae8d44316d05a: WebShell – ASPXspy (good.txt)

– 285b5f246f994b4650475db5143e4987: WebShell – Caidao (index.txt)

– 7e1a2828650e707d8142d526604f4061: BadPotato (bad.exe)

– 83b66aae624690e82c8e011e615bce59: BadPotato (bad520.exe)

– 5f3dd0514c98bab7172a4ccb2f7a152d: GodPotato (god3.exe)

– 1fdb1dd742674d3939f636c3fc4b761f: GodPotato (god4.exe)

– 493aaca456d7d453520caed5d62fdc00: PrintNotifyPotato (P2.exe)

– 493aaca456d7d453520caed5d62fdc00: PrintNotifyPotato (P3.exe)

– 7727070eb8c69773cafb09ce77492c27: PrintNotifyPotato (P4.exe)

– f7d53946b3ae7322cd018480a2f47de8: IIS LPE (iislpe.exe)

– 10cf4d43163ee395ddad1fe7e777e2c9: IIS LPE (iislpe1.exe)

– f222524766456936074f513cec2149a8: Cpolar (cpo.exe)

– d6f84855f212400314fb72d673aba27b: Frpc (F.exe)

– 62ba55ac729763037da1836b46cb84bc: Frpc (frpc.exe)

– 3c5905da1f3aecd2dccc05f6b76a1ca9: Frpc Config (frpc.txt)

– ce1f3b789b2aab2b2b833343f13b7c98: Lcx (99.exe)

– 371a2eb2800bb2beccc1a975f3073594: Lcx (Lcx.exe)

– 7abca4faa3609f86f89f1a32fe7bbcc6: UserAdder (UserAdd.exe)

– e8a7e8bb090da018b96aab3a66c7adeb: UserAdder Command (net.txt)

– 5d9464aba77e1830e1cf8d6b6e14aa55: UserAdder Command (useradd.bat)

Second Attack Case:-

– 71a6ba713f3f5c8e24c965487a86b5d4: WebShell – Chopper (zbngjv.aspx)

– 93abe2fcb964ec91de7d75c52d676d2d: WebShell – Chopper (bin.aspx)

– 2c3de1cefe5cd2a5315a9c9970277bd7: WebShell – Godzilla (aaa.ashx)

– 69c7d9025fa3841c4cd69db1353179cf: WebShell – Godzilla (aaa.asmx)

– 7871587d8de06edc81c163564ea4ea41: WebShell – awen (cmd.aspx)

– 10b6e46e1d4052b2ad07834604339b57: WebShell – Behinder (hi1.aspx)

– 5eeda9bfb83aacb9c3f805f5a2d41f3b: WebShell – Deleter (sklqbpbl.aspx)

– 5f3dd0514c98bab7172a4ccb2f7a152d: GodPotato (gp1.exe)

– 493aaca456d7d453520caed5d62fdc00: PrintNotifyPotato (pp.exe)

– 87562e70e958c0a0e13646f558a85d04: Privilege escalation tool – CVE-2021-1732 (aa.aspx)

– 8f7dfbec116017d632ca77be578795fd: Fscan (fscan.exe)

– 5dcf26e3fbce71902b0cd7c72c60545b: NetCat (nc.exe)

– 523613a7b9dfa398cbd5ebd2dd0f4f38: NetCat (nc64.exe)

– d76e1525c8998795867a17ed33573552: EarthWorm (ew.exe)

– 5d93629fbc80fed017e1657392a28df4: Ladon (11.exe)

– e9cb6a37c43e0393d4c656bc9f6bf556: RingQ (ringq.exe)

– 705e5d7328ae381c5063590b4f5198da: CoinMiner downloader (gzrqo.aspx)

– b81577dbe375dbc1d1349d8704737adf: CoinMiner (aspx.exe)

C&C Server URLs

– 14.19.214[.]36:6666: NetCat

– 14.19.214[.]36:3333: NetCat

– 1.119.3[.]28:7455: Frpc

Download URLs

– hxxp://sinmaxinter[.]top:7001/services.zip: CoinMiner

– hxxp://sinmaxinter[.]top:7001/C3-server25.zip: CoinMiner

– hxxp://14.19.214[.]36:6666/pp.exe: PrintNotifyPotato

– hxxp://14.19.214[.]36/aa.aspx: Privilege escalation tool – CVE-2021-1732

– hxxp://14.19.214[.]36/fscan.exe: Fscan

– hxxp://14.19.214[.]36/ew.exe: EarthWorm

– hxxp://14.19.214[.]36/11.exe: Ladon

– hxxp://14.19.214[.]36/RingQ.exe: RingQ

– hxxp://45.130.22[.]219/aspx.exe: CoinMiner

– hxxp://192.210.206[.]76/sRDI.dat: CoinMiner

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