Certified: The Security+ Prepcast

When a cybersecurity incident occurs, there’s often a temptation to solve the problem and move on. Isolate the system. Remove the malware. Get things running again. But in some cases, that isn’t enough. Whether you’re dealing with a policy violation, an internal investigation, a legal matter, or a regulatory inquiry, the ability to preserve and handle digital evidence properly is critical. That’s where digital forensics comes into play. And today, we’re going to build the foundation by focusing on two of the most important components: legal holds and chain of custody.
Let’s start with legal holds. A legal hold is a formal instruction to preserve data because it may be relevant to current or potential litigation. The moment there is a reasonable expectation that data might be needed in a legal or investigative context, that data must be protected. That means halting any normal deletion or modification processes. No more auto-deleting email inboxes. No more overwriting of logs. No more reimaging of affected devices. The goal of a legal hold is to make sure the relevant digital evidence remains intact, accessible, and legally defensible.
Legal holds are typically issued by the legal department, but the actual responsibility for carrying them out falls to cybersecurity, IT, and operations teams. Once issued, the legal hold must be clearly communicated to everyone who has access to the data in question. This might include system administrators, helpdesk staff, HR personnel, or cloud platform managers. Everyone involved must understand that the data under hold cannot be altered, deleted, or moved without authorization. In some cases, even accessing the data without proper tracking can compromise its integrity as evidence.
Here’s a real-world example. Imagine a healthcare provider suspects that a former employee accessed patient records without proper authorization. The legal department is notified and issues a legal hold. The hold covers electronic health records, email communications, access logs, and workstation activity for that employee. The IT team disables any data retention limits on those systems, suspends account deletion policies, and takes forensic images of the employee’s device. By doing so, they ensure that the data is preserved exactly as it was at the time of the suspected activity. This becomes crucial later when investigators review the logs and determine whether patient privacy laws were violated.
Legal holds are not just about responding to lawsuits. They also apply to regulatory investigations, criminal cases, internal HR reviews, and contract disputes. If the organization has even a reasonable belief that the data might be needed in a future inquiry, the hold must be issued. And it must be followed.
Once a legal hold is in place, the organization must carefully manage access to the data and document every action taken from that point forward. That brings us to our second focus: chain of custody.
Chain of custody is the formal, documented process of tracking the handling of evidence from the moment it is identified until it is presented in a legal or investigative setting. It proves that the evidence has not been tampered with, altered, or mishandled. And without it, even perfectly preserved data can be challenged—or thrown out—in court.
Think of chain of custody like a baton in a relay race. Every time that baton changes hands, it’s logged. Who had it. When they had it. Why they had it. Where it was stored. And what was done with it. The moment there is a gap in that record, the integrity of the evidence comes into question.
Let’s take a simple example. A cybersecurity analyst identifies a suspicious file on a user’s workstation. Rather than deleting it or examining it live on the system, the analyst uses a write-blocked device to take an image of the hard drive. They record the date, time, system serial number, and hash value of the image file. That image is then sealed in a secure container, labeled with a case number, and placed in an evidence locker. Later, when another analyst begins reviewing the image, they sign for it and verify that the hash matches the original. Every time the evidence is moved, accessed, or reviewed, that information is logged.
This process might seem like overkill, especially in small environments. But in legal, regulatory, or even internal disciplinary investigations, these procedures are absolutely essential. If someone questions whether the evidence has been altered or whether someone else could have tampered with it, your chain of custody log becomes the only thing that proves otherwise.
Chain of custody applies to both physical and digital evidence. For a physical asset like a hard drive or a USB stick, that might mean sealed evidence bags, security tags, and lockable storage. For digital artifacts like log files or virtual machine snapshots, that means using cryptographic hash values, access control logs, and secure storage systems that track every change and retrieval.
Hashing is a critical component here. By generating a unique hash value—such as a SHA-256 hash—when the evidence is collected, you create a digital fingerprint. Anytime that evidence is accessed, copied, or transferred, the hash can be recalculated and compared to the original. If the values match, the evidence is unchanged. If they don’t, something happened—and that evidence may no longer be valid.
Here’s another example. A financial institution is investigating potential fraud in one of its regional branches. Security teams collect transaction logs, employee email archives, and surveillance video footage. Each piece of evidence is logged with a unique identifier and a hash value. The data is stored in a secure vault and only accessed by designated investigators. When the case goes to court six months later, the institution presents not just the evidence, but the full chain of custody documentation showing exactly how it was handled at every step. That documentation is what makes the evidence admissible and trustworthy.
One common mistake in digital forensics is breaking the chain without realizing it. This can happen when someone reviews a file directly on the live system instead of creating a forensic copy. Or when evidence is transferred informally via email or unsecured storage. Or when log files are rotated and overwritten before they’re collected. Each of these missteps introduces doubt, and doubt is the enemy of admissibility.
Strong chain of custody isn’t just about tools. It’s about culture. It means training your team to treat digital evidence with the same care they would apply to physical evidence in a criminal investigation. It means logging every action, securing every copy, and following procedures even when no one’s watching.
To summarize, legal holds and chain of custody are the foundation of trustworthy digital forensics. Legal holds ensure that data is preserved when there’s reason to believe it may be needed in legal or investigative proceedings. Chain of custody ensures that once that data is collected, its integrity is maintained through every step of the process. Together, these practices turn raw data into reliable evidence—evidence that can stand up in a courtroom, a boardroom, or a compliance audit.
For the Security Plus exam, expect questions about when a legal hold should be issued, what constitutes a valid chain of custody, and how to handle digital evidence correctly. You may be asked to identify flaws in an evidence handling scenario or determine whether an action preserves admissibility. Review terms like preservation order, evidence integrity, cryptographic hash, evidence locker, and forensic imaging—they’re all key elements of this domain.
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