Certified: The GIAC GCIL Audio Course

In this episode, we’re going to learn how to classify an incident by attack type in a way that helps you set the right response goals quickly, even when information is incomplete. Beginners often hear classification and think it means picking a label for a report, like naming a folder, but in incident leadership, classification is a decision tool. The label you choose shapes what your team looks for next, what you protect first, who you involve, and which mistakes you work hardest to avoid. If you misclassify, you can waste time, take the wrong containment action, or communicate the wrong risk to stakeholders. If you classify well, even at a high level, you reduce confusion and make the response feel coordinated instead of reactive. The goal here is not to memorize a huge list of attacks, but to build the habit of identifying the likely attack type from clues, and then translating that type into practical response goals that fit the moment.

To make classification useful, you need a simple definition that keeps you grounded. Classification is the process of assigning an incident to a meaningful attack type based on evidence and context so the team can choose goals and priorities. Attack type is not the same as severity, because severity is about how serious the situation is, while type is about what kind of behavior is happening. Two incidents can be the same type but different severity, like a small account compromise versus a widespread account compromise, and confusing the two leads to bad decisions. Classification is also not a final verdict, because early classification is often provisional, meaning you start with your best fit and adjust as evidence improves. That flexibility is a leadership strength, not weakness, because incidents evolve and new facts can overturn early assumptions. The key is to choose a type that helps your team act responsibly now, while staying honest about uncertainty. When you treat classification as a living decision, you can move forward without pretending you know more than you do.

A helpful beginner approach is to classify by the kind of harm or control being targeted, because that makes the clues easier to interpret. Some attack types target identity, like stealing credentials and taking over accounts. Some target availability, like denial-of-service floods that make services unusable. Some target data, like unauthorized access leading to exposure or exfiltration. Some target system integrity, like malware that changes or encrypts files, or a compromise that installs persistence to control systems over time. Some target trust and communication, like phishing that tricks users into giving secrets or approving actions they shouldn’t. When you listen to an incident description, try to hear which of those targets is most central right now. That target suggests the likely type, and the likely type suggests what your response goals should be in the first hour. This is how you go from confusing symptoms to a structured plan.

Let’s start with a very common type for modern incidents: credential-based compromise, where attackers use stolen or guessed credentials to access systems as a legitimate user. Credential compromise can come from phishing, password reuse, credential stuffing, or insider misuse, but the unifying idea is that access happens through identity. The response goals for this type typically include confirming whether access is truly unauthorized, limiting the attacker’s ability to continue using the account, and assessing what the account could reach. That means containment goals often revolve around access control actions, like disabling accounts, enforcing resets, or tightening authentication requirements, but also doing so in a way that avoids locking out critical operations unnecessarily. Another goal is to identify whether this is a single account issue or a broader pattern across multiple accounts, because that changes severity and resource needs. If you classify correctly as credential compromise, you focus on identity signals, privilege scope, and lateral movement risk, rather than wasting time chasing unrelated system anomalies. The exam often tests this because identity incidents are frequent and the wrong reaction can either cause business disruption or allow ongoing attacker access.

Another major attack type is malware infection, which is a broad category that can include many behaviors, from annoying adware to serious remote control. Malware is best understood as unwanted software that performs harmful or unauthorized actions, often including persistence, data collection, or remote command execution. When you classify an incident as malware, your response goals include limiting spread, preserving evidence, and restoring trust in affected systems. That means containment might involve isolating affected systems from the network or restricting what they can reach, while simultaneously collecting key information needed to understand what the malware did. A common beginner mistake is to jump straight to cleaning everything without preserving evidence, which can destroy clues needed for scoping and accountability. Another mistake is to assume one infected device is the whole story, when the malware might be a symptom of broader compromise. A good classification encourages you to ask, how did it get here, what else might be affected, and what trust decisions do we need to make before bringing systems back. The attack type leads you toward integrity and persistence concerns, which is different from an identity-only incident.

Ransomware is a specific malware-related type that deserves separate attention because the response goals are unique and often urgent. Ransomware is typically about encrypting data or systems and then demanding payment, often paired with threats to leak stolen data, which creates a double pressure of availability and confidentiality. When you classify an incident as ransomware, your first response goals usually include stopping further encryption, protecting backups, and determining how widespread the impact is. Protecting backups is critical because backups represent recovery options, and ransomware operators often try to damage or delete them. Another goal is to establish what systems are still trustworthy and what systems may be unsafe to reconnect, because ransomware can be paired with broader compromise. Communication and stakeholder involvement also become central quickly, because ransomware incidents often have major business impact and potential legal or regulatory consequences if data was exposed. If you misclassify ransomware as a generic outage, you may delay containment and allow more encryption, which is disastrous. A correct classification pushes you toward rapid containment, careful evidence preservation, and coordinated recovery planning.

Now consider denial-of-service, often referred to as Distributed Denial of Service (D D o S), which is primarily an availability attack. In D D o S, the attacker overwhelms services or networks with traffic or requests so legitimate users cannot access them. The response goals here are different from credential compromise or malware because the primary harm is service disruption, not necessarily unauthorized access to data. That means your goals often include restoring availability, protecting critical services, and distinguishing between real demand spikes and hostile traffic patterns. Communication to stakeholders is also important, because outages create immediate business impact and customer frustration. A beginner trap is to treat D D o S as if it automatically implies data theft, which can lead to unnecessary internal panic and misdirected investigation. Another trap is to focus only on technical mitigation while ignoring business continuity needs, like alternate service paths or clear customer updates. Correct classification helps you set goals that match the attack’s nature: maintain service, stabilize systems, and validate whether any separate compromise is occurring alongside the availability assault. This is a good example of how type drives the right mindset.

Phishing is another common attack type, and it often acts as a gateway to other incidents rather than being the final event. Phishing is a social engineering approach where attackers use deceptive messages to trick people into revealing information, clicking malicious links, or approving actions they shouldn’t. If you classify an incident as phishing, your response goals include limiting spread of the message, identifying who interacted with it, and determining what the attacker gained. That could mean assessing credential exposure, malware infection risk, or unauthorized financial actions, depending on what the phishing attempt targeted. Communication goals become important internally, because you want to warn users without causing confusion or blame, and you want to capture reports quickly to improve detection. A common misconception is that phishing is only about bad links, when it can also be about convincing someone to transfer money, change account settings, or reveal sensitive data directly. Correct classification keeps you focused on the human interaction path, the potential credential impact, and the need for rapid user-focused containment measures. It also encourages you to think about prevention improvements later, like training and email controls, but only after immediate risk is stabilized.

Data exposure and exfiltration is another attack type category that is heavily tested in leadership contexts because it changes obligations and communications. Data exposure means sensitive data was accessible to unauthorized parties, even if you do not yet have proof it was downloaded. Exfiltration means data was actually moved out of the organization, which is a stronger claim that usually requires stronger evidence. When you classify an incident as data exposure or exfiltration, response goals include confirming what data is involved, limiting further access, preserving evidence, and involving the right stakeholders early, such as legal and communications leaders. The response often requires careful language, because saying data was stolen when you only know it was exposed can cause unnecessary harm, while minimizing a real exfiltration event can be equally damaging. Another goal is to understand how the exposure occurred, such as misconfiguration, compromised credentials, or insider misuse, because that affects containment. Correct classification here is less about naming a flashy attacker and more about accurately identifying the data risk and the obligations that may follow. The exam often rewards caution, accuracy, and disciplined escalation when data is at stake.

Insider-related incidents are another type worth understanding, because the response goals include both technical control and careful process. Insider incidents involve authorized access being used in an unauthorized way, either intentionally or accidentally, such as data misuse, sabotage, or policy violations. Classification can be tricky because insiders can look like normal users in logs, and the organization must handle the situation with fairness and control to avoid legal and cultural harm. Response goals often include limiting risky access, preserving evidence, and involving the appropriate internal stakeholders who manage personnel and legal considerations. A beginner mistake is to treat every suspicious action as malicious insider behavior without evidence, which can lead to accusations and trust damage. Another mistake is to ignore the possibility of insider misuse because it feels uncomfortable, allowing ongoing harm. Correct classification focuses you on evidence-based assessment, role-appropriate escalation, and controlled communication, because insider situations are high-sensitivity and require discipline. It also reminds you that insider incidents can be paired with compromised accounts, so classification may evolve as you validate whether the user truly performed the actions.

Supply chain and third-party incidents are another type category that often confuses beginners because the attacker might not be inside your environment at first. Supply chain incidents involve compromise of a vendor, service provider, software dependency, or update mechanism that then affects your organization. If you classify an incident as supply chain related, your response goals include determining the blast radius, understanding shared responsibilities, and coordinating with external parties without losing control of your own containment and communication. A key goal is to identify what systems depend on the compromised component and whether you can isolate or mitigate that dependency. Another goal is to avoid assuming the vendor will solve it quickly, because your organization still has to manage risk and continuity. A beginner trap is to treat a vendor incident as not your problem, which delays internal mitigation and leaves you exposed. Another trap is to overreact by shutting down broad systems without understanding dependency relationships, causing unnecessary disruption. Correct classification pushes you toward coordinated external engagement and internal scoping, which is a distinct leadership challenge.

Now let’s connect classification to the practical skill of reading clues in a scenario, because the exam will rarely announce the attack type in plain terms. Clues can be behavioral, like unusual login times, repeated failed logins, or access from unfamiliar locations, which often suggests credential attack patterns. Clues can be operational, like sudden service unavailability or resource exhaustion, which might suggest D D o S or a disruptive system failure. Clues can be integrity-related, like unexpected file encryption, changed configurations, or new suspicious processes, which can point toward malware or ransomware. Clues can be communication-related, like multiple users reporting suspicious emails or prompts to reauthenticate, which can suggest phishing. Clues can be data-related, like unusual large transfers, access to sensitive repositories, or external sharing changes, which can suggest exposure or exfiltration. A helpful habit is to identify the strongest clue, then ask what attack type best explains it, and then ask what evidence would confirm or contradict that classification. This keeps you from locking onto the first idea without validation.

Once you choose a likely attack type, setting response goals becomes much easier because goals should match the type’s core harm. For identity-based incidents, goals emphasize access control, validation, and privilege scoping. For availability incidents, goals emphasize service restoration, stability, and distinguishing malicious pressure from normal demand. For integrity incidents like malware or ransomware, goals emphasize containment of spread, evidence preservation, and trust restoration. For data incidents, goals emphasize limiting exposure, understanding affected data, stakeholder involvement, and careful communications. For supply chain incidents, goals emphasize scoping dependencies, coordinating externally, and managing internal mitigation without waiting passively. Beginners often set goals that are too broad, like fix everything, which leads to scattered effort. Attack-type classification narrows the target, making goals specific enough to guide tasking and communication. In exam questions, the best next step often aligns with these type-driven goals, even when details are fuzzy.

It’s also important to remember that classification can be layered, because real incidents can involve multiple attack types at once. A phishing email can lead to credential compromise, which can lead to data exposure, which can lead to ransomware, and each phase shifts priorities. If you treat classification as a single permanent label, you might keep chasing the first layer while the incident evolves. A better approach is to classify the current dominant risk and update as evidence changes, while keeping an eye on plausible next moves an attacker might take. This is where understanding Tactics, Techniques, and Procedures (T T P) becomes helpful, because it trains you to think about how one action leads to another without requiring deep technical detail. You don’t need to be a forensic specialist to understand that stolen credentials can enable broader access, and broader access can enable data theft or system disruption. The exam often tests this adaptive thinking by presenting new facts mid-scenario, and your best answers will reflect a willingness to update classification and goals based on confirmed evidence.

To close, classifying an incident by attack type is one of the fastest ways to turn uncertainty into a coherent response plan, because it connects clues to goals. The key is to treat classification as a decision tool, not a paperwork label, and to choose a type that helps your team act responsibly in the present while staying honest about what is not yet confirmed. Different attack types create different priorities, whether you’re dealing with identity compromise, malware, ransomware, D D o S, phishing, data exposure, insider risk, or supply chain complications. When you can read scenario clues, select a plausible attack type, and set goals that match the core harm, you reduce chaos and improve both decision-making and communication. This is exactly what incident leadership looks like in practice, and it is exactly the kind of thinking the GCIL incident leader role expects you to demonstrate under exam conditions. Keep your classification evidence-based, keep your goals aligned to the type, and be ready to adjust as new facts appear.