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Nov 22, 2021
Microsoft Exchange Vulnerability - CVE-2021-42321
THE THREAT eSentire has identified publicly available Proof-of-Concept (PoC) exploit code, for the critical Microsoft Exchange vulnerability CVE-2021-42321. CVE-2021-42321 was announced as part of Microsoft’s November Patch Tuesday release. Exploitation would allow a remote threat actor, with previous authentication, to execute code on vulnerable servers. Prior to the patch release, Microsoft…
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eSentire is The Authority in Managed Detection and Response Services, protecting the critical data and applications of 1000+ organizations in 70+ countries from known and unknown cyber threats. Founded in 2001, the company’s mission is to hunt, investigate and stop cyber threats before they become business disrupting events.
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Oct 28, 2021
Telarus and eSentire Expand Partnership to Safeguard Enterprises Globally Against Business Disrupting Ransomware and Zero-Day Attacks
London, UK and Sydney, Australia– Oct. 28, 2021 - eSentire, recognized globally as the Authority in Managed Detection and Response (MDR), today announces the expansion of its partnership with Telarus, the largest privately-held distributor of business cloud infrastructure and contact centre services. Building on their mutual success across North America, Telarus will bring eSentire’s Managed…
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Blog — Mar 24, 2017

Cyber threats 101: how to prevent file-based malware and botnets

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Malware is malicious code that’s used to obtain unrestricted access to a victim machine. This makes the ability to harvest and take advantage of victim data effortless and is usually automated.

In the current cybersecurity threat landscape, we see most botnets propagating via exploits and file-based malware. Anything that touches the disk has the ability to be blocked via access controls on the host.

New techniques utilize more than just binaries to execute malicious code, which is why there is a need for execution control. The main techniques we see botnets attempting to grow is through malware utilizing JavaScript payloads, standard binaries, macros and PowerShell payloads.

Delivery Mechanisms

The notable delivery techniques for malware is through exploitation (exploit kits and malvertising) and social engineering (tricking users into opening bad software). Defense in depth strategies generally focus on preventing the exploit/malware from landing via network access controls. If a threat actor is able to get initial code execution on a machine it is up to the access controls on the host system to prevent successful compromise.

Code Execution

The most popular ways to execute code on a host system is through binary executables, scripts and shellcode. Shellcode can be utilized in many ways and it often does not need to touch disk as such blocking shellcode will not be covered in this post. Examples of some common code execution methods is below:

Common Binary Executables

Common Script Code

Code execution has many layers at which it can be stopped. For example, there are ways to stop interpreters from interpreting script code on a windows system.

In the majority of attacks, we see threat actors utilizing a benign piece of software (dropper) to download the malicious payload which executes and carries out the malicious instructions. Common file formats that are utilize to execute the initial instructions can be seen below:

Prevention Mechanisms:

One of the most effective ways to protect against compromise is by limiting what someone has the ability to do when they get onto a machine. Consider enforcing these best practices within your organization:


There are many security features that can be implemented at the host level to harden a Windows system. The best practices suggested here address just a few configuration changes that can be made to make it harder for a threat actor to execute code.

Although not all of these recommendations are applicable to all environments, they can be used as an information resource for those who are looking to implement hardening changes within their environment.

In many cases the delivery mechanisms are generally the same for most malware strains. Ransomware is a form of malware that is utilized by threat actors to hold the victims of an attack hostage to extort money. The delivery mechanisms described here are commonly used to deliver the malicious payload, which results in full compromise.

The ability to stop the initial execution of malicious code will stop the execution of a malicious payload - effectively stopping its ability compromise.

When it comes to malware-based attacks, you can’t count on technology alone to detect and block the attack. Unwitting employees can deploy malware by clicking on a malicious attachment. It’s in these situations that leveraging managed detection and response (MDR) capabilities is essential. Through advanced hunting and anomaly detection, MDR is able to detect and block malware-based attacks even after they’ve breached perimeter defenses. At eSentire we call this micro-incident response.

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Kurtis Armour
Kurtis Armour Senior Security Strategist

Kurtis is a Senior Security Strategist at eSentire, where he focuses on securing client networks, vulnerability research and exploit development. In addition to ongoing research efforts, Kurtis regularly speaks at industry conferences.