Managed XDR Exposes Spear-Phishing Campaign Targeting Hospitality Industry Using RedLine Stealer

Recently, we noticed a spike in the number of emails received by one of our customers. After further investigation, we found that three other customers in the hospitality industry were also affected. We observed that most of the emails had subject lines that attempt to catch victims’ attention: “help,” “requesting for assistance,” “route map,” “this is me from booking.com,” and “booking reservation.” Some of the emails also had a “Re:” in the subject line, which attempts to trick victims into thinking that they are reading a reply to an email thread.

The email copy contained text composed to lure targets, mostly hotel staff, into clicking a Dropbox link that dropped malware. Also used were Bitly-shortened URLs that redirected to Dropbox links that contained malicious files.

Figure 1. Sample email subjects and URLs

Unfortunately, some users were lured into unwittingly downloading malware via these malicious emails. During analysis, we noticed the file sizes of the extracted malware samples. Malware file sizes typically range from just a kilobyte to a few megabytes. However, the samples we obtained had atypically large file sizes, ranging from 494.7 MB to as large as 929.7 MB.

Technical analysis

We analysed a sample spear-phishing email sent by a malicious actor pretending to be an older adult who is asking for someone from the hotel to verify if his route is correct. At first glance, it appears to be a typical one-off spam email that contains a shortened URL that drops malware. In a sample spear-phishing email we analysed, a malicious actor pretends to be an elderly man asking for help from hotel staff to validate his overland route. He provides a shortened link, supposedly to images of his route for hotel staff to validate.

Figure 2. Initial email and victim’s response

As previously mentioned, we believe this to be a spear-phishing campaign that specifically targets members of the hospitality industry. In Figure 3, the malicious actor responds to the hotel employee in a polite and helpless manner to influence them to select a link that does not lead to a route diagram but actually leads to the malware payload.

Figure 3. The malicious actor’s response

Unfortunately, the employee fell victim to this spear-phishing campaign. Using the Trend Micro Vision One™ solution, we saw that the employee opened the link using outlook.exe, which downloaded a zip file named “Christian-Robinson-Route.zip.” This zip file contained a file with a double extension, “Christian-Robinson-Route.jpg.exe,” which is a tactic that malicious actors use to trick victims into downloading and executing malicious files.

Figure 4. Execution chain of the employee accessing a Bitly-shortened URL using Outlook

The extracted and launched “Christian-Robinson-Route.jpg.exe” file triggered a chain of events. Figure 5 shows the entire execution chain as observed in Trend Micro Vision One:

Figure 5. Spear-phishing campaign execution chain as seen in Vision One

The campaign can be divided into four stages:

Figure 6. The spear-phishing campaign’s four stages

Stage 1: “Christian-Robinson-Route.jpg.exe” drops “setupsoftwarefile_v7.7.exe”

“Christian-Robinson-Route.jpg.exe” is a cabinet file that contains a large amount of padding. This is an old technique used by malware authors to bypass antivirus detection, sandbox analysis, and YARA rules. The paddings we observed were either random bytes or repeated strings, which is possibly because of the builder or packer that was used to add the large overlays. As previously mentioned, the samples we obtained range from 494.7 MB to as large as 929.7 MB in size.

Figure 7. Padding on “Christian-Robinson-Route.jpg.exe” that is used to inflate the file and evade detection

Upon execution, it drops an MSIL file, “setupsoftwarefile_v7.7.exe”, and executes it via cmd.exe. This file will then decrypt and execute a PowerShell script.

Figure 8. “setupsoftwarefile_v7.7.exe” decrypting and executing a PowerShell script

Stage 2: The PowerShell script retrieves an encrypted file from hxxp://45.93.201[.]62/docs/

The PowerShell script will connect to hxxp://45.93.201[.]114/docs/fzLJerifqJwFtnjbrlnJPNrfnupnYg[.]txt to get another MSIL file named Ferriteswarmed.exe, which will then be AES-decrypted, GZIP-decompressed, and loaded in PowerShell via.NET reflective loading. It has a debugger check that will exit once a debugger is found.

Figure 10. HTTP response from hxxp://45.93.201[.]114/docs/fzLJerifqJwFtnjbrlnJPNrfnupnYg[.]txt

Based on the samples we have obtained, other encrypted files are hosted on hxxp://45.93.201[.]114/docs/.

Stage 3: The “Ferriteswarmed.exe” MSIL file decrypts image files that form RedLine Stealer payload

A portable executable (PE) file’s resource section contains the resource information of a module. In many cases, it shows icons and images that are part of a file’s resources. In this case, the new MSIL file, “Ferriteswarmed.exe,” will decrypt another payload that is disguised as encrypted images from its resources — the Redline Stealer. The RedLine Stealer will then be injected into “aspnet_compiler.exe”.

Figure 13. The Redline Stealer payload disguised as encrypted image files

Stage 4: RedLine Stealer sends stolen info to C&C server

Using Trend Micro Vision One, we were able to observe the kind of information that RedLine Stealer collects, which include operating system, video controller, processor, antivirus, processes, and disc drive data via the Windows Management Instrumentation (WMI). The stolen data is sent to its C&C server, 77.73.134[.]13:12785.

Figure 14. RedLine Stealer’s stolen data via WMI

It is also capable of collecting data from browsers, cryptocurrency wallets, VPN applications, and other installed applications such as Discord.

Security Scorecard published a detailed report about RedLine Stealer that includes a comprehensive list of data that this infostealer collects. We observed a marked difference in the RedLine Stealer samples they analysed compared to ours — their malware samples created a BasicHttpBinding object that uses HTTP as the transport for sending SOAP messages to its C&C server, while the samples we obtained use NetTcpBinding for message delivery. The commands in our samples are also not named.

Figure 15. RedLine Stealer sample that uses NetTcpBinding for message delivery

Security recommendations and Trend Micro solutions

Email-related threats are becoming increasingly sophisticated and harder to spot. Back in the day, bad grammar and an exaggerated sense of urgency were enough tell-tale signs of malicious emails. Nowadays, malicious actors have evolved to mimic the voice and tone of the character they’re trying to pretend to be and at times, are prepared to play the long con.

To successfully combat spam or phishing threats, organisations must give their employees the necessary tools, resources, and training to help them better flag malicious emails that can lead to data breaches and ransomware attacks. Organisations can benefit from Trend Micro’s Phish Insight, which provides effective and automated real-world phishing simulations and customised training campaigns.

Trend Micro’s comprehensive XDR solution applies the most effective expert analytics to the deep data sets collected from Trend Micro solutions across the enterprise, making faster connections to identify and stop attacks. Powerful artificial intelligence (AI) and expert security analytics correlate data from customer environments and Trend Micro’s global threat intelligence to deliver fewer, higher-fidelity alerts, leading to better, early detection. One console with one source of prioritised, optimised alerts supported with guided investigation simplifies the steps to achieving a full understanding of the attack path and impact on the organisation.

Trend Micro Service One™ allows organisations to be more resilient with 24/7/365 premium support, managed XDR, and incident response services. This service also provides automated solution updates and upgrades, on-demand training, best practise guides, and access to cybersecurity and CISO experts.

The Trend Micro Apex One™ solution offers threat detection, response, and investigation within a single agent. Automated threat detection and response provide protection against an ever-growing variety of threats, including fileless and ransomware. And an advanced endpoint detection and response (EDR) toolset, strong security information and event management (SIEM) integration, and an open application programming interface (API) set provide actionable insights, expanded investigative capabilities, and centralised visibility across the network.

Trend Micro Cloud One™ – Endpoint Security and Workload Security protect endpoints, servers, and cloud workloads through unified visibility, management, and role-based access control. These services provide specialised security optimised for your diverse endpoint and cloud environments, which eliminate the cost and complexity of multiple point solutions. Meanwhile, the Trend Micro Cloud One™ – Network Security solution goes beyond traditional intrusion prevention system (IPS) capabilities, and includes virtual patching and post-compromise detection and disruption as part of a powerful hybrid cloud security platform.

The Trend Micro™ Deep Discovery™ Email Inspector solution detects, blocks, and analyses malicious email attachments. Ransomware-carrying spam can thus be stopped from even reaching employees’ inboxes. It also cheques and blocks access to malicious URLs embedded in emails. Its custom sandbox technology can also detect and block ransomware that comes in the guise of macros. This solution is deployed inline of message delivery and blocks malicious spear-phishing messages. It analyses known and unknown patterns, and uses reputation analysis to detect the latest ransomware variants, such as WannaCry, and targeted attacks.

IOCs

File name	SHA-256	Detection name	File size
Booking-id669392.jpg.scr	bf803adb5695fce143062e6f51980d46537167b7a9e0e85ad13a999e35bd0466	Trojan.Win32.REDLINE.JKRC	576.7 MB
Booking-Maps-id785392.exe	6c5a4a8b7554000d5ab5221c43f25f093ba6a37c6b2511335e002f333c5af6c4	Trojan.MSIL.REDLINE.V	701.6 MB
Booking-Maps-id938192.exe	6c5a4a8b7554000d5ab5221c43f25f093ba6a37c6b2511335e002f333c5af6c4	Trojan.MSIL.REDLINE.V	701.6 MB
Booking-Maps-id9382194.jpg.scr	bf803adb5695fce143062e6f51980d46537167b7a9e0e85ad13a999e35bd0466	Trojan.Win32.REDLINE.JKRC	576.7 MB
Christia-Robinson-Route.jpg.exe	9bacf20a00f73124039c4476d600e70293ae60d1d1d28290a63000b510f313f0	Trojan.Win32.REDLINE.EOC	929.7 MB
Corel Contract.pdf.exe	62e7d750df3bb49f9535e8b4ba91d5ba8f5c655a0027643b52a3d9ffb0b64208	TrojanSpy.MSIL.NEGASTEAL.RJAHSPE	750 MB
GoogleMaps.exe	af23af4d4b3ba82c76a50bb631b4aca8d98e9a1560000d5c6fce39977cb9d362	NOT_DETECTED	784.7 MB
GoogleMaps(2).exe	84910fcdcb2edb3feeb3307bee0e6b33fc91caf8de344a3be71452b04b4595f0	TrojanSpy.MSIL.AURORA.AA	494.7 MB
GooglePhoto-MilanaZinowiewa.jpg.exe	6cbe9be190f521408438262d0c7f2ccbfab32a6df558cec2a264285fdfffe5c2	Trojan.Win32.REDLINE.JKRC	765.3 MB
id328493942-Booking_info.jpg.scr	53af2c266c7f18e7c1ab16460d3c09d773fae93ac0a840fa83a30cc1020d1019a	TrojanSpy.MSIL.REDLINE.DCRB	898.6 MB
id695838211-Booking-Confirmation.exe	4f1c1565afc782e688945c07a486205c59d43a98ae577c5d065bfed9a47a983d	Trojan.Win32.REDLINE.JKRC	741.2 MB
Maps-Google-Adolv.jpg.exe	b5d8caa15cbf53d002edc6194abd0de43e4a139cc04f9703ae7bfc397bca66c8	TrojanSpy.MSIL.REDLINE.DCRD	769.9 MB
Michael-Martinez-Photo-Route.jpg.exe	9bacf20a00f73124039c4476d600e70293ae60d1d1d28290a63000b510f313f0	Trojan.Win32.REDLINE.EOC	929.7 MB
photo-my-and-wife-passport.exe	43328f774db70b98c4cbe83cc3be18de20a29b073b483eec49c64c6c301e4079	TrojanSpy.Win32.REDLINE.DCRC	816.4 MB
Route-Map.png.exe	1b5f1e505e57b9915418f251f9c2343302f0737bdd85126666db56a27f0142f2	TrojanSpy.MSIL.REDLINE.JNCSF	888 MB
Stephan_Fruehauf_sparkasse_receipt_15.01.2023.pdf.exe	b83e50fa2c5c54e027f3bfe859e2a69e883bbb0080fed20aca176f77ad120fa1	Trojan.Win32.REDLINE.EOC	662.2 MB

Managed XDR Exposes Spear-Phishing Campaign Targeting Hospitality Industry Using RedLine Stealer

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