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What is a Trojan?
7/14/2023 - Brian O'Neill

For a threat actor to initiate a cyberattack, they first need to find a way through the front gates of a target network. Threat actors perpetually seek out fresh vulnerabilities and test new attack vectors in pursuit of this goal, attempting to stay ahead of the fast-evolving cybersecurity curve.

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Through all the persistent innovation in cyberattacks, however, the art of disguising threats in plain sight remains among the most effective network-breaching methods. Successfully tricking a user on a target network into accessing malicious content can rapidly snowball into a virus or malware download, and once that download occurs, subsequent attacks can be carried out within that user’s device (or, in some cases, multiple devices attached to the same network) to steal data or use their IP address for further malicious activity.

Named after the infamous wooden “gift” that famously penetrated the walls of Troy more than 4,000 years ago, Trojan Horse threats (Trojans) are a long-standing and prolific cyberattack vector, accounting for a high volume of successful breach attempts on Windows operating systems.

Understanding Trojans

Trojans are a type of malware specifically designed to appear as a normal, legitimate file or program to the naked eye. Unlike viruses, which are often capable of executing without the help of user download, trojans require the victim to willingly access their contents before injecting a malicious payload. They’re most often used as a method for installing other types of malware, like viruses, worms, or ransomware, onto a victim’s device.

Trojans are very frequently spread through emails which spoof trusted external contacts or information sources. The Trojan malware itself is usually included in a file attachment, which will quickly download and install its contents once the victim clicks on the file to open it. These same types of infected files can often be found on malicious websites which aim to gain a victim’s trust by appearing like other websites that legitimate files are commonly downloaded from (imagine, for example, a fake research website promoting a free download of their report on recent marketing trends). In addition, trojans can hide alongside application downloads which are usually safe, “piggybacking” on legitimate software to sneak onto a victim’s device.

Common Types of Trojans

Because Trojans can be used to carry a wide variety of threats, they can be used to achieve an equally diverse set of malicious outcomes.

One of the most common and damaging types of trojan is a Backdoor Trojan, which attackers can use to directly take control of a computer. Once the attacker gains unrestricted access to a computer, they can download valuable data to an external device and take a variety of other malicious actions.

Trojans are also frequently used as a precursor for carrying out Distributed Denial of Service (DDoS) attacks on a separate target. Attackers often carry out DDoS attacks by flooding a target server (typically one operated by a large company or government organization) with requests, and they can assemble the required group of compromised devices by sending Trojans to victims via spam emails or through social media platforms.

Further, ransomware – an extremely common form of malware designed to hold valuable data hostage until a certain price is paid – is often installed onto a system using a Trojan as the initial attack vector.

Preventing Trojan Attacks

Preventing Trojan attacks on any network of devices starts with training users to identify threatening content. Illegitimate emails can usually be identified with a careful glance at the email address or message body, and file attachments should only ever be accessed when they come from completely verifiable and trusted external locations. In addition, users on any network should always exercise extreme caution when downloading files or applications directly from a seemingly legitimate website. Malicious sites are often flagged by up-to-date web browsers and tracked by reputable cybersecurity organizations. Developers and system administrators can also protect their network and file storage locations from Trojans by frequently updating their security policies and building security redundancy in particularly sensitive areas.

Detecting Trojans with the Cloudmersive Virus Scan API

The Cloudmersive Virus Scan API can be deployed to detect trojans at the network edge in both forward or reverse proxies (Cloudmersive Shield), and it can be deployed to detect trojans stored within cloud storage instances (Cloudmersive Storage Protect) like AWS S3, Azure Blob, SharePoint Online Site Drive, and Google Cloud Storage. Both the Basic and Advanced Virus Scan API iterations provide multi-threat scanning coverage against viruses, malware, trojans, ransomware and spyware, referencing a continuously updated list of more than 17 million virus and malware signatures. The Advanced Virus Scan API iteration is also capable of detecting hidden content threats like executables, macros, scripts, unsafe archives, and more, providing customizable threat rules in the API request body.

For more information about how the Cloudmersive Virus Scan API can protect your system against trojans and other threats, please do not hesitate to reach out to a member of our sales team.

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