--- title: "What Is a Trojan and How Does It Work? | DMARC Report" description: "A Cybersecurity Guide by DMARCReport The shift to mandatory email authentication in 2024-2025 was the biggest change in email security in a decade." image: "https://dmarcreport.com/og/blog/what-is-a-trojan-and-how-does-it-work.png" canonical: "https://dmarcreport.com/blog/what-is-a-trojan-and-how-does-it-work/" --- Quick Answer Cyber threats continue to evolve, and one of the most deceptive types of malware organizations face today is the Trojan. Unlike many other forms of malicious software, Trojans rely heavily on deception and user interaction to infiltrate systems. They often appear harmless or even beneficial at first glance, but once installed they can quietly execute harmful actions in the background. Related: [Free DMARC Checker](/tools/dmarc-checker/) ·[How to Create an SPF Record](/tools/spf-record-generator/) ·[SPF Record Format](/blog/spf-format-checker-dos-and-donts-for-email-authentication/) Share [ ](https://www.linkedin.com/sharing/share-offsite/?url=undefined%2Fblog%2Fwhat-is-a-trojan-and-how-does-it-work%2F "Share on LinkedIn") [ ](https://twitter.com/intent/tweet?text=What%20Is%20a%20Trojan%20and%20How%20Does%20It%20Work%3F&url=undefined%2Fblog%2Fwhat-is-a-trojan-and-how-does-it-work%2F "Share on X/Twitter") [ ](https://www.facebook.com/sharer/sharer.php?u=undefined%2Fblog%2Fwhat-is-a-trojan-and-how-does-it-work%2F "Share on Facebook") [ ](https://reddit.com/submit?url=undefined%2Fblog%2Fwhat-is-a-trojan-and-how-does-it-work%2F&title=What%20Is%20a%20Trojan%20and%20How%20Does%20It%20Work%3F "Share on Reddit") [ ](mailto:?subject=What%20Is%20a%20Trojan%20and%20How%20Does%20It%20Work%3F&body=Check out this article: undefined%2Fblog%2Fwhat-is-a-trojan-and-how-does-it-work%2F "Share via Email") ![What Is a Trojan and How Does It Work?](https://media.mailhop.org/dmarcreport/images/2022/04/dmarc-record-6071.jpg) ## A Cybersecurity Guide by DMARCReport > The shift to mandatory email authentication in 2024-2025 was the biggest change in email security in a decade, says Brad Slavin, General Manager of DuoCircle. Google, Yahoo, and Microsoft all requiring DMARC means there’s no inbox provider left that accepts unauthenticated bulk mail. Every organization needs to adapt. Cyber threats continue to evolve, and one of the most deceptive types of malware organizations face today is the Trojan. Unlike many other forms of malicious software, Trojans rely heavily on deception and **user interaction to infiltrate systems**. They often appear harmless or even beneficial at first glance, but once installed they can quietly execute harmful actions in the background. At DMARCReport, we frequently analyze email-borne threats and domain-based attacks, and Trojans remain a common payload used by [cybercriminals](https://incyber.org/en/article/united-states-amounts-stolen-by-cybercriminals-up-33/). Understanding what Trojans are, how they operate, and how they spread is essential for both individuals and organizations that want to strengthen their cybersecurity posture. This guide explains Trojan malware in detail, including how it works, the different types of Trojans, and how you can prevent and remove them. ## What Is a Trojan? A Trojan, often called a **Trojan horse**, is a type of malware that disguises itself as legitimate software in order to trick users into installing it. Once the malicious program is executed, it can perform a wide range of harmful activities , including stealing data, damaging files, or giving attackers remote access to a device. The name “Trojan” originates from the famous story of the Trojan Horse in ancient Greek mythology. In the legend, Greek soldiers hid inside a giant wooden horse that was presented as a gift to the city of Troy. When the horse was brought inside the city walls, the hidden soldiers emerged and attacked. Trojan malware follows the same concept. It appears safe or useful on the outside, but inside it contains malicious code designed to compromise the victim’s device or network. Unlike viruses or worms, Trojans **do not self-replicate**. Instead, they rely on [social engineering](https://www.securityweek.com/cyber-insights-2026-social-engineering/) techniques to convince users to download and run them. ![Dmarc record](https://media.mailhop.org/dmarcreport/images/2026/03/dmarc-record-6651.jpg) ## How Trojans Typically Spread Cybercriminals distribute Trojan malware through several common channels. In most cases, the attacker manipulates the victim into interacting with a [malicious file or link](https://www.csoonline.com/article/4143937/resumes-with-malicious-iso-attachments-are-circulating-says-aryaka.html). ## Phishing Emails Email remains one of the most popular delivery methods for Trojans. Attackers send emails that appear to come from trusted sources such as banks, coworkers, or service providers. These emails often contain attachments or links that install the Trojan when opened. Because the message looks legitimate, users may unknowingly execute the malicious file. ## Fake Software Downloads Trojans are frequently hidden inside pirated software, cracked applications, or fake updates. When the victim installs the program, the Trojan installs simultaneously . ## Compromised Websites Sometimes Trojans are delivered through compromised or malicious websites. Visiting such sites may trigger automatic downloads or redirect users to infected installers. ## Messaging and Social Media Attackers may also spread Trojans through messaging platforms or social media by sending links that appear to lead to legitimate downloads, games, or documents. The common factor in all these scenarios is deception. Trojans depend on the \*\*victim’s trust and interaction \*\*to gain access to the system. ![What is dmarc](https://media.mailhop.org/dmarcreport/images/2026/03/what-is-dmarc-6651.jpg) ## How a Trojan Works Once a Trojan enters a device, it can perform many different malicious activities depending on its design. The typical Trojan lifecycle often follows several stages. ## 1\. Disguise and Delivery The Trojan first appears as a legitimate file, application, or attachment. Examples include invoices, software installers, or browser updates. Because the file looks normal, users may not suspect anything unusual. ## 2\. Execution by the User Unlike self-spreading malware, a Trojan requires the victim to execute it. This might involve opening an attachment, installing software, or clicking a download link. Once the file is executed, the malicious code activates. ## 3\. Silent Installation After execution, the Trojan installs itself quietly on the device. Many Trojans configure themselves to run automatically every time the system starts. At this stage, the victim often notices no obvious warning signs. ## 4\. Communication with the Attacker Many Trojans connect to a remote [command-and-control server](https://www.techtarget.com/whatis/definition/command-and-control-server-CC-server) operated by the attacker. Through this connection, the attacker can send commands to the infected device. This allows cybercriminals to control infected machines remotely. ## 5\. Malicious Activity Depending on the Trojan’s purpose, it may perform several harmful actions, including: - Stealing login credentials - Monitoring user activity - Recording keystrokes - Downloading additional malware - Disrupting system performance Some Trojans remain hidden for long periods, collecting information quietly before attackers use the stolen data. ## What Trojans Can Do After Infection The damage caused by Trojan malware depends on its functionality and the attacker’s goals. Some of the most common **consequences include**: ## Data Theft Trojans often target sensitive information such as login credentials, credit card numbers, or confidential business data. ## Remote System Control Certain Trojans allow attackers to control a victim’s computer remotely. This enables cybercriminals to access files, install additional malware, or manipulate system settings . ## Installation of Other Malware A Trojan can act as a gateway for other malicious programs such as ransomware, spyware, or botnets. ## Surveillance Some Trojans capture screenshots, record keystrokes, or activate microphones and webcams to monitor victims without their knowledge. ## System Disruption Infected systems may experience performance issues, crashes, or corrupted files due to malicious processes running in the background. For organizations, Trojan infections can lead to [data breaches](https://cybermagazine.com/news/ericsson-data-breach), operational disruptions, financial losses, and legal consequences. ![Dmarc record generator](https://media.mailhop.org/dmarcreport/images/2026/03/dmarc-record-generator-6651.jpg) ## Types of Trojan Malware _Trojans exist in many forms, each designed for a specific type of attack_. Below are some of the most common categories seen in **modern cyber threats**. ## Backdoor Trojans Backdoor Trojans create hidden access points that allow attackers to control a system remotely. Once a backdoor is established, cybercriminals can send commands or install additional malware without the victim’s knowledge. ## Downloader Trojans These Trojans are designed primarily to download and install other malicious programs. Once installed, they fetch additional malware from remote servers. ## DDoS Trojans [Distributed Denial-of-Service (DDoS)](https://www.infosecurity-magazine.com/news/ddos-escalation-frequency-power/) Trojans are used to attack websites or online services. Infected devices become part of a botnet that sends large volumes of traffic to overwhelm a target server. ## Ransom Trojans Ransom Trojans encrypt files or lock systems and demand payment in exchange for restoring access. ## Rootkit Trojans [Rootkit Trojans](https://www.darkreading.com/cyberattacks-data-breaches/-obama-trojan-rides-coattails-of-president-elect) hide malicious files or processes inside a system to avoid detection by security software. ## SMS Trojans These Trojans primarily target mobile devices. They can send premium SMS messages, intercept texts, or collect sensitive mobile data. Each type of Trojan has a different purpose, but they all rely on deception and hidden execution\*\*. ## Trojans on Mobile Devices Although Trojans originally targeted desktop computers, mobile devices have increasingly become a major target. Cybercriminals often distribute Trojan-infected mobile apps disguised as legitimate applications. Once installed, these apps may steal personal information, intercept messages, or perform [fraudulent transactions](https://www.cnbc.com/2024/07/26/ai-and-machine-learning-helped-visa-combat-40-billion-in-fraud-activity.html). In some cases, Trojan apps also send premium SMS messages or subscribe users to expensive services without their consent. Because smartphones often contain banking apps, personal data, and authentication tools, mobile Trojans can cause significant damage. ## Warning Signs of a Trojan Infection Detecting Trojan infections can be difficult because they are designed to remain hidden. However, certain warning signs may indicate that a system has been compromised. Some common indicators include: - Unexpected system slowdowns - Unknown programs running in the background - Unusual network activity - Browser redirects or pop-ups - Disabled security software Although these symptoms do not always indicate a Trojan infection, they should prompt further investigation. ![Dmarc report](https://media.mailhop.org/dmarcreport/images/2026/03/dmarc-report-6651.jpg) ## How to Prevent Trojan Malware Preventing Trojan infections requires a combination of technical security controls and user awareness. Here are some effective strategies recommended by cybersecurity experts. ## Be Careful With Email Attachments Avoid opening attachments or clicking links from unknown or suspicious senders. Even messages that appear to come from trusted contacts should be verified . ## Download Software From Trusted Sources Only install applications from official websites or reputable app stores. Avoid pirated software and unofficial downloads. ## Use Security Software Reliable antivirus and endpoint protection tools can detect and remove many types of Trojan malware. ## Keep Systems Updated Regularly updating [operating systems](https://en.wikipedia.org/wiki/Operating%5Fsystem) and software helps patch vulnerabilities that attackers may exploit. ## Use Email Authentication Tools Technologies such as [SPF](https://dmarcreport.com/blog/how-spf-can-help-organizations-in-improving-email-security-and-thwarting-spam-phishing-and-email-spoofing/), [DKIM](https://dmarcreport.com/blog/dkim-explained-how-dkim-works-and-why-is-dkim-important-for-organizations/), and DMARC help organizations prevent phishing emails that distribute malware. Implementing strong email authentication policies can significantly reduce Trojan delivery attempts. At DMARCReport, we strongly recommend \*\*implementing email security controls alongside endpoint protection. ![Create dmarc record](https://media.mailhop.org/dmarcreport/images/2026/03/create-dmarc-record-6651.jpg) ## How to Remove Trojan Malware If a Trojan infection is suspected, quick action is necessary to prevent further damage. ## Disconnect From the Internet Disconnecting the device from the network helps prevent attackers from continuing to control the system. ## Run Security Scans Use reputable antivirus or malware removal tools to scan and remove malicious programs. ## Delete Suspicious Programs If you identify the infected software, uninstall it immediately. ## Restore From Backup In severe cases, restoring the system from a clean backup may be the safest solution. Organizations should also investigate the source of the infection to prevent future attacks. ## Final Thoughts Trojans remain one of the most deceptive and dangerous forms of malware in modern cybersecurity\*\*. By disguising themselves as legitimate files or software, they exploit human trust to gain access to devices and networks. Once inside a system, a Trojan can steal sensitive data, install additional malware, or give attackers remote control over infected devices. For businesses and individuals alike, the best defense is a combination of awareness, strong security practices, and reliable protective tools . At [DMARCReport](https://dmarcreport.com/), we emphasize the importance of email authentication and threat detection as part of a comprehensive cybersecurity strategy. Since many Trojan attacks begin with phishing emails, strengthening email security is a critical step toward preventing these infections. Understanding how Trojans work is the first step toward defending against them - and ensuring that your systems remain secure in an **increasingly complex digital landscape**. ## Topics [ dkim ](/tags/dkim/)[ DMARC ](/tags/dmarc/)[ dmarc record ](/tags/dmarc-record/)[ dns record ](/tags/dns-record/)[ SPF ](/tags/spf/) ![Vishal Lamba](https://media.mailhop.org/dmarcreport/images/team/vishal-lamba.jpg) [ Vishal Lamba ](/authors/vishal-lamba/) Content Specialist Content Specialist at DMARC Report. Writes vendor-specific email authentication guides and troubleshooting walkthroughs. [LinkedIn Profile →](https://www.linkedin.com/in/vishal-lamba/) ## Take control of your DMARC reports Turn raw XML into actionable dashboards. Start free - no credit card required. [Start Free Trial](https://app.dmarcreport.com/) [Check Your DMARC Record](/tools/dmarc-checker/) ## Related Articles [ Foundational 14m Add TXT Record on Namecheap (SPF, DKIM & DMARC) - 2026 Mar 5, 2025 ](/blog/add-txt-record-on-namecheap-a-complete-dns-guide/)[ Foundational 12m Adding SPF Records To Your Domain For Outlook Email Authentication Sep 25, 2025 ](/blog/adding-spf-records-to-your-domain-for-outlook-email-authentication/)[ Foundational 9m Answering Your Webinar Questions: Email Security - From The Desk Of DMARCReport Dec 2, 2025 ](/blog/answering-webinar-questions-email-security-dmarcreport-desk-insights-guide/)[ Foundational 12m Best DMARC Checker Tools Comparing Dmarcian, Mxtoolbox, And Proofpoint Dec 1, 2025 ](/blog/best-dmarc-checker-tools-comparing-dmarcian-mxtoolbox-and-proofpoint/) ```json {"@context":"https://schema.org","@type":"Organization","@id":"https://www.wikidata.org/wiki/Q138898167","name":"DMARC Report","url":"https://dmarcreport.com","logo":{"@type":"ImageObject","url":"https://dmarcreport.com/images/dmarcreport-logo.png"},"description":"DMARC reporting and email authentication management. Monitor aggregate and forensic DMARC reports, analyze authentication results, and enforce DMARC policies across all your domains.","parentOrganization":{"@type":"Organization","@id":"https://www.wikidata.org/wiki/Q138883901","name":"DuoCircle LLC","url":"https://www.duocircle.com","sameAs":["https://www.wikidata.org/wiki/Q138883901","https://www.crunchbase.com/organization/duocircle-llc","https://www.linkedin.com/company/duocircle","https://github.com/duocircle"],"subOrganization":[{"@type":"Organization","@id":"https://www.wikidata.org/wiki/Q138898167","name":"DMARC Report","url":"https://dmarcreport.com"},{"@type":"Organization","@id":"https://www.wikidata.org/wiki/Q138897474","name":"AutoSPF","url":"https://autospf.com"},{"@type":"Organization","@id":"https://www.wikidata.org/wiki/Q138897912","name":"Phish Protection","url":"https://www.phishprotection.com"}]},"sameAs":["https://www.wikidata.org/wiki/Q138898167","https://www.linkedin.com/company/duocircle","https://x.com/duocirclellc","https://www.g2.com/products/dmarc-report/reviews","https://github.com/duocircle","https://www.crunchbase.com/organization/duocircle-llc","https://www.trustradius.com/products/duocircle/reviews"],"aggregateRating":{"@type":"AggregateRating","ratingValue":"4.8","reviewCount":"470","bestRating":"5","worstRating":"1","url":"https://www.g2.com/products/dmarc-report/reviews"},"contactPoint":{"@type":"ContactPoint","contactType":"customer support","url":"https://dmarcreport.com/support/"},"knowsAbout":["DMARC","DMARC Reporting","DMARC Aggregate Reports","DMARC Forensic Reports","Sender Policy Framework","DKIM","Email Authentication","Email Security","DNS Management","Email Deliverability"]} ``` ```json {"@context":"https://schema.org","@type":"WebSite","name":"DMARC Report","url":"https://dmarcreport.com","description":"DMARC reporting and email authentication management. Monitor aggregate and forensic DMARC reports, analyze authentication results, and enforce DMARC policies across all your domains.","publisher":{"@type":"Organization","name":"DMARC Report","url":"https://dmarcreport.com","logo":{"@type":"ImageObject","url":"https://dmarcreport.com/images/dmarcreport-logo.png"},"description":"DMARC reporting and email authentication management. Monitor aggregate and forensic DMARC reports, analyze authentication results, and enforce DMARC policies across all your domains.","parentOrganization":{"@type":"Organization","@id":"https://www.wikidata.org/wiki/Q138883901","name":"DuoCircle LLC","url":"https://www.duocircle.com","sameAs":["https://www.wikidata.org/wiki/Q138883901","https://www.crunchbase.com/organization/duocircle-llc","https://www.linkedin.com/company/duocircle","https://github.com/duocircle"],"subOrganization":[{"@type":"Organization","@id":"https://www.wikidata.org/wiki/Q138898167","name":"DMARC Report","url":"https://dmarcreport.com"},{"@type":"Organization","@id":"https://www.wikidata.org/wiki/Q138897474","name":"AutoSPF","url":"https://autospf.com"},{"@type":"Organization","@id":"https://www.wikidata.org/wiki/Q138897912","name":"Phish Protection","url":"https://www.phishprotection.com"}]}}} ``` ```json [{"@context":"https://schema.org","@type":"BlogPosting","headline":"What Is a Trojan and How Does It Work?","description":"A Cybersecurity Guide by DMARCReport The shift to mandatory email authentication in 2024-2025 was the biggest change in email security in a decade.","url":"https://dmarcreport.com/blog/what-is-a-trojan-and-how-does-it-work/","datePublished":"2026-03-13T10:40:43.000Z","dateModified":"2026-04-16T15:53:43.000Z","dateCreated":"2026-03-13T10:40:43.000Z","author":{"@type":"Person","@id":"https://dmarcreport.com/authors/vishal-lamba/#person","name":"Vishal Lamba","url":"https://dmarcreport.com/authors/vishal-lamba/","jobTitle":"Content Specialist","description":"Vishal Lamba writes DMARC Report's how-to guides and vendor-specific configuration walkthroughs. His work focuses on step-by-step implementation guides for major email platforms (Google Workspace, Microsoft 365, SendGrid, Mimecast, Proofpoint, Brevo, and others), troubleshooting common SPF and DMARC errors, and translating RFC-level specifications into practical deployment procedures for IT administrators.","image":"https://media.mailhop.org/dmarcreport/images/team/vishal-lamba.jpg","knowsAbout":["SPF Vendor Configuration","Email Platform Integrations","SPF Troubleshooting","Technical Documentation","Step-by-Step Guides"],"worksFor":{"@type":"Organization","name":"DMARC Report","url":"https://dmarcreport.com"},"sameAs":["https://www.linkedin.com/in/vishal-lamba/"]},"publisher":{"@type":"Organization","@id":"https://www.wikidata.org/wiki/Q138898167","name":"DMARC Report","url":"https://dmarcreport.com","logo":{"@type":"ImageObject","url":"https://dmarcreport.com/images/dmarcreport-logo.png"},"description":"DMARC reporting and email authentication management. Monitor aggregate and forensic DMARC reports, analyze authentication results, and enforce DMARC policies across all your domains.","parentOrganization":{"@type":"Organization","@id":"https://www.wikidata.org/wiki/Q138883901","name":"DuoCircle LLC","url":"https://www.duocircle.com","sameAs":["https://www.wikidata.org/wiki/Q138883901","https://www.crunchbase.com/organization/duocircle-llc","https://www.linkedin.com/company/duocircle","https://github.com/duocircle"],"subOrganization":[{"@type":"Organization","@id":"https://www.wikidata.org/wiki/Q138898167","name":"DMARC Report","url":"https://dmarcreport.com"},{"@type":"Organization","@id":"https://www.wikidata.org/wiki/Q138897474","name":"AutoSPF","url":"https://autospf.com"},{"@type":"Organization","@id":"https://www.wikidata.org/wiki/Q138897912","name":"Phish Protection","url":"https://www.phishprotection.com"}]},"sameAs":["https://www.wikidata.org/wiki/Q138898167","https://www.linkedin.com/company/duocircle","https://x.com/duocirclellc","https://www.g2.com/products/dmarc-report/reviews","https://github.com/duocircle","https://www.crunchbase.com/organization/duocircle-llc","https://www.trustradius.com/products/duocircle/reviews"],"aggregateRating":{"@type":"AggregateRating","ratingValue":"4.8","reviewCount":"470","bestRating":"5","worstRating":"1","url":"https://www.g2.com/products/dmarc-report/reviews"},"contactPoint":{"@type":"ContactPoint","contactType":"customer support","url":"https://dmarcreport.com/support/"},"knowsAbout":["DMARC","DMARC Reporting","DMARC Aggregate Reports","DMARC Forensic Reports","Sender Policy Framework","DKIM","Email Authentication","Email Security","DNS Management","Email Deliverability"]},"mainEntityOfPage":{"@type":"WebPage","@id":"https://dmarcreport.com/blog/what-is-a-trojan-and-how-does-it-work/"},"articleSection":"foundational","keywords":"dkim, DMARC, dmarc record, dns record, SPF","wordCount":1727,"image":{"@type":"ImageObject","url":"https://media.mailhop.org/dmarcreport/images/2022/04/dmarc-record-6071.jpg","caption":"What Is a Trojan and How Does It Work?","width":900,"height":600},"speakable":{"@type":"SpeakableSpecification","cssSelector":[".answer-block","h1"]}}] ``` ```json {"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https://dmarcreport.com/"},{"@type":"ListItem","position":2,"name":"Blog","item":"https://dmarcreport.com/blog/"},{"@type":"ListItem","position":3,"name":"Foundational","item":"https://dmarcreport.com/foundational/"},{"@type":"ListItem","position":4,"name":"What Is a Trojan and How Does It Work?","item":"https://dmarcreport.com/blog/what-is-a-trojan-and-how-does-it-work/"}]} ```