May 2023’s Most Wanted Malware: New Version of Guloader Delivers Encrypted Cloud-Based Payloads

Check Point Research reported on a new version of shellcode-based downloader GuLoader featuring fully encrypted payloads for cloud-based delivery.  

Our latest Global Threat Index for May 2023 saw researchers report on a new version of shellcode-based downloader GuLoader, which was the fourth most prevalent malware. With fully encrypted payloads and anti-analysis techniques, the latest form can be stored undetected in well-known public cloud services, including Google Drive. Meanwhile, Qbot and Anubis are taking first place on their respective lists, and Education/Research remained the most exploited industry.

GuLoader is one of the most prominent downloader cybercriminals use to evade antivirus detection. With over three years of activity and ongoing development, the latest version employs a technique that replaces code in a legitimate process, enabling it to evade detection by process monitoring security tools. By utilizing a VBScript to download encrypted shellcode from the cloud, victims receive a less suspicious file, reducing the likelihood of triggering alerts. The use of encryption, raw binary format, and separation from the loader renders the payloads invisible to antiviruses, allowing threat actors to bypass antivirus protection and leverage Google Drive for storage. In some instances, these malicious payloads may remain active for extended periods of time.

Last month also saw both Qbot and Anubis taking first place on their respective lists. Despite efforts to slow down malware distribution by blocking macros in Office files, Qbot operators have been quick to adapt their distribution and delivery. It has recently been seen abusing a dynamic link library (DLL) hijacking flaw in the Windows 10 WordPad program to infect computers.

More often than not we are seeing cybercriminals exploiting tools available to the public to store and deliver malware campaigns. We can no longer blindly trust that the services we use will be completely secure, no matter how trustworthy the source may be. That is why we need to be educated on what suspicious activity looks like. Do not disclose personal information or download attachments unless you have verified that the request is legitimate and there is no malicious intent.

CPR also revealed that “Web Servers Malicious URL Directory Traversal” was the most exploited vulnerability, impacting 49% of organizations globally, followed by “Apache Log4j Remote Code Execution” impacting 45% of organizations worldwide. “HTTP Headers Remote Code Execution” was the third most used vulnerability, with a global impact of 44%.

Top malware families

*The arrows relate to the change in rank compared to the previous month.

Qbot was the most prevalent malware last month with an impact of 6% worldwide organizations, followed by Formbook with a global impact of 5% and AgentTesla with a global impact of 3%.

1. ↑ Qbot – Qbot AKA Qakbot is a multipurpose malware that first appeared in 2008. It was designed to steal a user’s credentials, record keystrokes, steal cookies from browsers, spy on banking activities, and deploy additional malware. Often distributed via spam email, Qbot employs several anti-VM, anti-debugging, and anti-sandbox techniques to hinder analysis and evade detection. Commencing in 2022, it emerged as one of the most prevalent Trojans.
2. ↑ Formbook – Formbook is an Infostealer targeting the Windows OS and was first detected in 2016. It is marketed as Malware as a Service (MaaS) in underground hacking forums for its strong evasion techniques and relatively low price. FormBook harvests credentials from various web browsers, collects screenshots, monitors and logs keystrokes, and can download and execute files according to orders from its C&C.
3. ↓ AgentTesla – AgentTesla is an advanced RAT functioning as a keylogger and information stealer, which is capable of monitoring and collecting the victim’s keyboard input, system keyboard, taking screenshots, and exfiltrating credentials to a variety of software installed on a victim’s machine (including Google Chrome, Mozilla Firefox and the Microsoft Outlook email client).
4. ↑ GuLoader – GuLoader is a downloader that has been widely used since December 2019. When it first appeared, GuLoader was used to download Parallax RAT but has been applied to other remote access trojans and info-stealers such as Netwire, FormBook, and Agent Tesla.
5. ↓ Emotet – Emotet is an advanced, self-propagate and modular Trojan. Emotet once used to be employed as a banking Trojan, and recently is used as a distributor to other malware or malicious campaigns. It uses multiple methods for maintaining persistence and Evasion techniques to avoid detection. In addition, it can be spread through phishing spam emails containing malicious attachments or links.
6. ↔ XMRig – XMRig is open-source CPU mining software used to mine the Monero cryptocurrency. Threat actors often abuse this open-source software by integrating it into their malware to conduct illegal mining on victims’ devices.
7. ↑ NJRat – NJRat is a remote accesses Trojan, targeting mainly government agencies and organizations in the Middle East. The Trojan has first emerged in 2012 and has multiple capabilities: capturing keystrokes, accessing the victim’s camera, stealing credentials stored in browsers, uploading and downloading files, performing process and file manipulations, and viewing the victim’s desktop. NJRat infects victims via phishing attacks and drive-by downloads, and propagates through infected USB keys or networked drives, with the support of Command & Control server software.
8. ↑ Lokibot – First identified in February 2016, LokiBot is a commodity infostealer with versions for both the Windows and Android OS. It harvests credentials from a variety of applications, web browsers, email clients, IT administration tools such as PuTTY and more. LokiBot is sold on hacking forums and it is believed that its source code was leaked, thus allowing numerous variants to appear. Since late 2017, some Android versions of LokiBot include ransomware functionality in addition to their infostealing capabilities.
9. ↓ NanoCore – NanoCore is a Remote Access Trojan that targets Windows operating system users and was first observed in the wild in 2013. All versions of the RAT contain basic plugins and functionalities such as screen capture, crypto currency mining, remote control of the desktop and webcam session theft.
10. ↓ Remcos – Remcos is a RAT that first appeared in the wild in 2016. Remcos distributes itself through malicious Microsoft Office documents, which are attached to SPAM emails, and is designed to bypass Microsoft Windows UAC security and execute malware with high-level privileges.

Top Attacked Industries Globally

Last month, Education/Research remained in first place as the most exploited industry globally, followed by Government/Military and Healthcare.

1. Education/Research
2. Government/Military
3. Healthcare

 Top exploited vulnerabilities

Last month, “Web Servers Malicious URL Directory Traversal” was the most exploited vulnerability, impacting 49% of organizations globally, followed by “Apache Log4j Remote Code Execution” impacting 45% of organizations worldwide. “HTTP Headers Remote Code Execution” was the third most used vulnerability, with a global impact of 44%.

1. ↔ Web Servers Malicious URL Directory Traversal – There exists a directory traversal vulnerability on different web servers. The vulnerability is due to an input validation error in a web server that does not properly sanitize the URI for the directory traversal patterns. Successful exploitation allows unauthenticated remote attackers to disclose or access arbitrary files on the vulnerable server.
2. ↔ Apache Log4j Remote Code Execution (CVE-2021-44228) – A remote code execution vulnerability exists in Apache Log4j. Successful exploitation of this vulnerability could allow a remote attacker to execute arbitrary code on the affected system.
3. ↔ HTTP Headers Remote Code Execution (CVE-2020-10826,CVE-2020-10827,CVE-2020-10828,CVE-2020-13756) – HTTP headers let the client and the server pass additional information with an HTTP request. A remote attacker may use a vulnerable HTTP Header to run arbitrary code on the victim machine.
4. ↑ MVPower DVR Remote Code Execution – A remote code execution vulnerability exists in MVPower DVR devices. A remote attacker can exploit this weakness to execute arbitrary code in the affected router via a crafted request.
5. ↑ Dasan GPON Router Authentication Bypass (CVE-2018-10561) – An authentication bypass vulnerability exists in Dasan GPON routers. Successful exploitation of this vulnerability would allow remote attackers to obtain sensitive information and gain unauthorized access into the affected system.
6. ↑ D-Link Multiple Products Remote Code Execution (CVE-2015-2051) – A remote code execution vulnerability exists in multiple D-Link products. Successful exploitation of this vulnerability could allow a remote attacker to execute arbitrary code on the affected system.
7. ↓ OpenSSL TLS DTLS Heartbeat Information Disclosure (CVE-2014-0160,CVE-2014-0346) – OpenSSL TLS DTLS Heartbeat Information Disclosure. The vulnerability, aka Heartbleed, is due to an error when handling TLS/DTLS heartbeat packets. An attacker can leverage this vulnerability to disclose memory contents of a connected client or server.
8. ↓ Command Injection Over HTTP (CVE-2021-43936,CVE-2022-24086) – A command Injection over HTTP vulnerability has been reported. A remote attacker can exploit this issue by sending a specially crafted request to the victim. Successful exploitation would allow an attacker to execute arbitrary code on the target machine.
9. ↔ PHP Easter Egg Information Disclosure (CVE-2015-2051) – An information disclosure vulnerability has been reported in the PHP pages. The vulnerability is due to incorrect web server configuration. A remote attacker can exploit this vulnerability by sending a specially crafted URL to an affected PHP page.
10. ↑ F5 BIG-IP Remote Code Execution (CVE-2021-22986) – A remote code execution vulnerability exists in F5 BIG-IP devices. Successful exploitation of this vulnerability could allow a remote attacker to execute arbitrary code on the affected system.

Top Mobile Malwares

Last month Anubis rose to first place as the most prevalent Mobile malware, followed by AhMyth and Hiddad.

1. Anubis – Anubis is a banking Trojan malware designed for Android mobile phones. Since it was initially detected, it has gained additional functions including Remote Access Trojan (RAT) functionality, keylogger, audio recording capabilities and various ransomware features. It has been detected on hundreds of different applications available in the Google Store.
2. AhMyth – AhMyth is a Remote Access Trojan (RAT) discovered in 2017. It is distributed through Android apps that can be found on app stores and various websites. When a user installs one of these infected apps, the malware can collect sensitive information from the device and perform actions such as keylogging, taking screenshots, sending SMS messages, and activating the camera, which usually used to steal sensitive information.
3. Hiddad – Hiddad is an Android malware which repackages legitimate apps and then releases them to a third-party store. Its main function is to display ads, but it can also gain access to key security details built into the OS.

Check Point’s Global Threat Impact Index and its ThreatCloud Map is powered by Check Point’s ThreatCloud intelligence. ThreatCloud provides real-time threat intelligence derived from hundreds of millions of sensors worldwide, over networks, endpoints and mobiles. The intelligence is enriched with AI-based engines and exclusive research data from Check Point Research, the intelligence and research Arm of Check Point Software Technologies.