Trojan

What is a Trojan?

A Trojan (or Trojan Horse) is malicious software that disguises itself as legitimate, useful software to trick users into downloading and executing it. Unlike viruses and worms, Trojans don't self-replicate but rely on social engineering to spread.

How Trojans Work

Infection Process

• Disguise – Masquerades as legitimate software (games, utilities, documents)
• Distribution – Spread through email attachments, downloads, USB drives
• Execution – User unknowingly runs the malicious code
• Installation – Establishes persistence and hides from detection

Common Disguises

• Fake software updates – Mimics legitimate update notifications
• Cracked software – Promises free versions of paid software
• Document files – Malicious macros in Word/Excel files
• Mobile apps – Fake versions of popular applications

Types of Trojans

Remote Access Trojans (RATs)

• Backdoor access – Provides remote control of infected systems
• Keylogging – Captures keystrokes and passwords
• Screen capture – Records user activity
• File manipulation – Upload, download, delete files

Banking Trojans

• Form grabbing – Captures banking credentials
• Web injection – Modifies banking websites
• Session hijacking – Steals active banking sessions
• SMS interception – Captures 2FA codes

Downloader Trojans

• Secondary payload – Downloads additional malware
• Update mechanism – Receives new malicious code
• Modular design – Can add new capabilities remotely

DDoS Trojans

• Botnet recruitment – Enlists systems in attack networks
• Traffic generation – Floods targets with requests
• Distributed attacks – Coordinates multiple infected systems

Detection and Prevention

Technical Detection

• Behavioral analysis – Monitor for suspicious activities
• Sandboxing – Execute in isolated environments
• Signature detection – Known malware patterns
• Heuristic analysis – Suspicious code patterns

Prevention Strategies

• User education – Security awareness training
• Email filtering – Block malicious attachments
• Web filtering – Prevent access to malicious sites
• Application whitelisting – Only allow approved software
• Regular updates – Keep systems and software patched

Analysis and Response

Static Analysis

• File examination – Analyze without execution
• String analysis – Extract readable text and URLs
• PE analysis – Examine executable structure
• Hash comparison – Check against known malware databases

Dynamic Analysis

• Sandbox execution – Monitor behavior in safe environment
• Network monitoring – Track communication attempts
• Registry monitoring – Watch for persistence mechanisms
• File system monitoring – Track file creation and modification

Best Practices

• Verify software sources – Download from official websites
• Use antivirus software – Keep definitions updated
• Enable UAC – User Account Control on Windows
• Regular backups – Protect against data loss
• Network monitoring – Detect unusual traffic patterns
• Incident response plan – Prepare for infections