How to use Time Travel Analysis to reverse engineer a malware

Reverse engineers work tirelessly to dissect ransomware, stealers, packers, and advanced persistent threats (APTs). The job requires staying ahead of attackers, understanding how threats evolve, and finding ways to outsmart them. But modern malware isn’t just malicious; it’s built to resist analysis.

We had the opportunity to work closely with a skilled malware analyst. For security reasons, we’ll call him Andrew. As we collaborated, we saw firsthand how even experienced professionals struggle with the same recurring challenges:

• Malware constantly mutates to evade detection.
• Multi-stage payloads are hidden behind layers of obfuscation.
• Encrypted C2 communications make network analysis incredibly difficult.

Some samples were so intricate that even powerful tools like decompilers, disassemblers, and debuggers weren’t enough. Debugging sessions turned into a frustrating loop of restarting, retracing steps, and dealing with malware designed to waste analysts' time.

This is Andrew’s story, but if you’ve ever spent hours (or days) debugging a malware sample, it might feel like your story too.

Meet Andrew, a malware reverse engineer

Andrew specializes in analyzing malicious files, from ransomware and stealers to post-exploitation toolkits and Remote Access Trojans (RATs). His goal isn’t just to understand what malware does but also to extract intelligence, determining how it operates, whether it connects to known threats, and, if possible, identifying its origin.

Like most reverse engineers, he starts with standard tools: a disassembler, decompiler, or debugger. These work well for simpler cases where static analysis is enough to reveal a malware’s behavior. But the moment malware introduces layers of obfuscation, anti-debugging techniques, or encrypted communications, things get significantly harder.

That’s when the real challenges begin.

Challenges in malware reverse engineering

Andrew frequently encounters malware specifically designed to slow down or block analysis. These are some of the biggest obstacles:

• Obfuscated execution chains that require multiple stages of unpacking.
• Sophisticated anti-debugging techniques that detect analysis attempts.
• Encrypted C2 communications that make it nearly impossible to recover payloads or extract meaningful intelligence.
• Self-modifying code that changes during execution, preventing analysts from capturing a clean sample.

With traditional debugging methods, breaking down these types of malware can take days or even weeks. Debugging sessions must be restarted repeatedly, with analysts retracing their steps each time, trying to capture fleeting execution details before they disappear.

For Andrew, these challenges weren’t occasional, they were the norm. He needed a better way to analyze malware without getting stuck in an endless debugging cycle.

Andrew explains:

"A typical case involves reversing the encryption algorithms used in the malware and recovering the C2 communication protocol. An extremely challenging example is reversing the Rhadamanthys stealer. The threat from this malware is complex because packers are used, the payload launch kill chain is very long (with a dropper, downloader, and several layers of encrypted shellcodes), the initial stages check the environment for sandboxing and debugging, the code runs in the context of different processes, the payload is loaded dynamically from C2 and encrypted in a picture file steganographically, and so on.

My task is not just to get an unpacked image of the payload (which is not very difficult, although this image won't run), but to be able to debug it and understand every step of the chain. Reversing some of the code fragments further with standard analysis utilities is a difficult, time-consuming task. With standard tools, to reverse the C2 communication protocol or the encryption algorithm for the malware config, you would need to repeat the debugging session from the beginning each time, moving up the call stack and seeing where the data came from in the network packet. Alternatively, you could start a debug session, create an image of the session in the virtual machine, wait for the encrypted data to be sent, move up the call stack, and roll back the image of the virtual machine, repeating this multiple times.”

Andrew needed a way to capture and analyze malware execution without constantly restarting his work. That’s when he discovered Time Travel Analysis.

How Time Travel Analysis changed everything

Time Travel Debugging (TTD), also known as Time Travel Analysis, enables reverse engineers to record a full execution trace of malware, then rewind and replay it without restarting the debugging session.

Instead of starting from scratch every time, Andrew could:

• Rewind and replay execution without triggering anti-debugging protections.
• Track obfuscation techniques and pinpoint encryption keys without worrying about changes between debugging sessions.
• Reverse-engineer the C2 communication protocol by tracing network packets back to their origin, even after encryption.
• Analyze malware behavior at different stages of execution, making it easier to unpack complex threats.

"With time travel analysis, I don’t have to restart my debugging session. I create a single trace and can track everything (decryption keys, function calls, memory modifications) without ever having to redo my work." - Andrew says.

The result? Less time wasted on setup and repetition, and more time focusing on what really matters: understanding the malware.

Using esReverse for Time Travel Debugging

While Time Travel Debugging is powerful, it needs a robust binary analysis tool to unlock its full potential. That’s where esReverse comes in.

With esReverse, Andrew was able to:

• Take full advantage of time travel analysis, recording a malware’s execution once and navigating through it forward and backward, eliminating the need for repeated debugging sessions.
• Easily integrate IDA Pro and other debuggers and decompilers into esReverse, allowing him to switch between tools seamlessly without leaving the platform.
• Use advanced taint analysis to track how data flows through memory and across function calls, making it easier to pinpoint encryption routines, unpacking mechanisms, and obfuscation techniques.
• Save and revisit his analysis, ensuring he could pause and resume work without losing context or having to start over from scratch.
• Access esReverse’s library of knowledge, with built-in tutorials, real-world use cases, and best practices to guide him through complex analysis challenges.

With esReverse, Andrew wasn’t just analyzing malware — he was controlling it.

"Instead of fighting through endless debugging sessions, I now reverse-engineer malware efficiently, track vulnerabilities, and extract intelligence faster than ever. Time Travel Debugging in esReverse has completely changed my workflow."

For professionals working in cyber threat intelligence, malware research, exploit investigation, or vulnerability analysis, tools like esReverse make it possible to tackle even the most complex malware samples without losing time on unnecessary debugging steps.

Request a demo today to see Time Travel Analysis in action!