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I. Introduction – "I am a Firewall"
My name is Firewall. Every morning, I wake up to the complex sounds of network traffic. Some are innocent; others try to sneak in through backdoors. My job is to let the good in and stop every dangerous packet. Today marks my 453rd day on duty guarding this server...
II. What Is a Firewall and What Does It Do?
A firewall is a digital guardian protecting computer networks from harmful external traffic. Using packet filtering methods, it inspects every data packet, tracks connection states (stateful inspection), and controls protocols and ports based on predefined rules.
Packet Filtering: Controls packet ingress and egress based on IP address, port number, and protocol, allowing or blocking traffic accordingly.
Stateful Inspection: Monitors previous connection states, permitting only expected and authorized traffic.
Proxy Firewall: Routes traffic through intermediary servers, masking the original IP for added security.
Application Layer Firewalls: Filters malicious traffic at the web application level, especially detecting and blocking threats over HTTP.
03:21 AM: Unknown IP tries to brute-force port 3389. RDP brute-force attack... Blocked immediately.
10:47 AM: SQL injection attempt through a web form. IPS activated, attack stopped.
02:09 PM: User clicked on a malicious .exe file. Fortunately, my UTM system was active.
06:35 PM: Port scan detected on port 624, attacker blocked.
IV. SQL Injection – A Sneaky and Dangerous Threat
SQL Injection is a powerful technique attackers use to manipulate database queries in web applications, aiming to steal, alter, or delete data. For example, a malicious user might input a crafted string in a login field to bypass authentication.
If the application lacks proper security, this can change the query logic and expose all user data.
Methods:
Tautology-Based Attacks: Inserts always-true conditions to bypass authentication.
Union Queries: Fetches combined data from multiple tables.
Blind SQL Injection: Extracts data by observing application behavior without error messages.
Error-Based Injection: Gathers info from database error messages.
Protection:
Web Application Firewall (WAF): Detects and blocks malicious SQL code.
Input Validation: Uses parameterized queries to sanitize all input data.
IPS: Stops suspicious queries in real-time.
1. DDoS (Distributed Denial of Service) Attacks
A DDoS attack aims to overwhelm a target system's resources by flooding it with excessive traffic. Attackers use botnets—networks of compromised machines—to send massive simultaneous requests.
Types:
Volumetric Attacks: Massive amounts of data packets sent (UDP Flood, ICMP Flood).
Protocol Attacks: Exhaust TCP connection resources (SYN Flood).
Application Layer Attacks: Flood HTTP requests to overload web servers.
Firewall and Protection:
Traffic analysis to detect abnormal patterns.
Rate limiting to restrict requests from specific IPs.
Blackhole routing to block attack traffic from reaching targets.
CDN and cloud-based Anti-DDoS solutions to filter traffic.
Stateful firewalls track TCP sessions and detect half-open connections.
Attackers try username and password combinations automatically to gain unauthorized access.
Methods:
Dictionary attacks: Trying common passwords.
Credential stuffing: Using leaked username/password pairs.
Hybrid attacks: Combining letters, numbers, and symbols.
Firewall and Protection:
Blocks repeated failed login attempts from the same IP.
CAPTCHA and MFA to hinder automated tries.
IPS detects and alerts on failed login patterns.
Malicious JavaScript runs in users’ browsers.
Example:
' OR '1'='1
Protection:
WAF blocks inputs containing malicious scripts.
Web apps sanitize all incoming data.
Content Security Policy (CSP) instructs browsers on allowed sources.
Communication is intercepted or altered by a malicious third party.
Methods:
ARP spoofing: Alters IP-MAC mappings.
DNS spoofing: Redirects DNS queries to fake addresses.
SSL stripping: Downgrades HTTPS to HTTP.
Protection:
Mandatory TLS/SSL encryption.
VPNs create secure tunnels.
IDS monitors suspicious ARP/DNS activity.
Port security limits switch port access.
Malicious software spreads via email attachments and downloads. Ransomware encrypts files, demanding ransom.
Protection:
UTM solutions offer multi-layered defense.
Email filters block malicious content.
Sandboxing isolates suspicious files.
Anomalous traffic and data exfiltration monitored.
Fake emails or websites impersonate real organizations to steal credentials.
Protection:
URL filtering and spam filters.
User awareness training.
Anti-phishing software.
Target unknown vulnerabilities before patches exist.
Protection:
Anomaly detection monitors abnormal behavior.
Rapid application of security patches.
Defense in depth strategy.
Manipulating DNS queries to redirect users or targeting DNS servers with DDoS.
Protection:
DNS filtering and rate limiting.
DNSSEC to validate DNS records.
Stealing session tokens to gain unauthorized access.
Protection:
Enforcing HTTPS.
Shortening session lifetimes and regularly refreshing tokens.
Authorized users cause harm intentionally or accidentally.
Protection:
Strict access controls.
Behavioral analytics to detect anomalies.
Detailed audit logging.
IDS (Intrusion Detection System): Monitors network traffic, detects attacks, and raises alerts.
IPS (Intrusion Prevention System): Includes IDS features and actively blocks attacks in real time.
Logs are the records of security events. Data collected via syslog and SIEM systems trace past attacks and provide early warnings of future threats.
"Every log entry holds clues to a future attack. Every byte whispers the secrets of the past."
VIII. Zero Trust Philosophy – Trust No One
Today’s “Zero Trust” model requires verifying everyone on the network, implementing micro-segmentation, and applying the principle of least privilege. Firewalls and other security layers support this model to create defense in depth.
IX. Closing – Another Night on Cyber Watch
11:59 PM. Today, 624 port scans, 3 SQL injections, and 1 DDoS attempt occurred... But the system remains safe. I am here, the first line of defense in the digital world, standing guard.