Security Log Analysis for SSH Brute Force, Firewall Blocks, Postfix Bounces and Dovecot Login Failures

Security investigations start in the logs

Many real security incidents begin as ordinary log lines. A failed SSH password attempt. A firewall deny event. A suspicious request for an admin path. A mail relay rejection. A Dovecot authentication failure. Each event can look harmless in isolation, but patterns across time, source IPs, users, ports, and services often reveal risk.

Security log analysis helps teams answer practical questions quickly: Are we under SSH brute force attack? Which IPs are scanning blocked ports? Did any login succeed after repeated failures? Are mail delivery errors caused by authentication, DNS, SPF, DKIM, or recipient rejection? Which raw lines prove the conclusion?

Why small teams need evidence-backed analysis

Large organizations may have a SIEM, dedicated detection engineers, and prebuilt dashboards. Smaller teams often have only raw files such as /var/log/secure, auth.log, syslog, firewalld logs, iptables logs, Postfix maillog, or Dovecot logs. During an incident, they need answers without building a full security pipeline first.

AskMyLogs is designed for that gap. It supports multiple operational and security log formats, extracts structured fields, and lets users ask natural-language questions while preserving raw evidence. The result is useful for incident triage, abuse review, hosting support, compliance notes, and post-incident reporting.

Detecting SSH brute force attempts

SSH brute force detection is one of the most common security log analysis tasks. Attackers and scanners often try many usernames across many servers. Typical usernames include root, admin, test, oracle, postgres, git, deploy, support, and ubuntu.

A good SSH auth log workflow should extract failed password attempts, invalid user entries, accepted logins, disconnects, source IPs, source ports, usernames, and timestamps. Once parsed, you can ask high-value questions: which source IP has the most failed logins, which usernames were targeted most often, were any valid users attacked, and did any successful login follow a burst of failures?

What matters more than raw failure count

A server may see hundreds of failed SSH attempts per day from internet-wide scanners. The important signal is context. A single source IP trying many invalid usernames is often low-grade automated scanning. Repeated attempts against a valid admin user are more serious. A successful login after failures deserves immediate review. A new source country or data center may be relevant depending on your environment.

AskMyLogs helps by grouping failures by source IP, username, event type, and time window. It also keeps the raw lines available so a team can verify the answer without trusting a black-box summary.

Analyzing firewall blocks and denied ports

Firewall logs show what traffic was blocked before it reached the application. They are useful for identifying scanners, exposed services, noisy networks, and blocked traffic patterns. Long-tail searches like analyze firewall deny logs by source IP or find top blocked ports in iptables logs usually come from teams deciding whether to block an IP range or investigate a specific service.

Start by grouping firewall events by action, destination port, source IP, protocol, and timestamp. A high volume of denied traffic to ports 22, 23, 3389, 445, 3306, 5432, or 6379 usually indicates scanning for common services. Repeated denies to an internal-only port may indicate a misconfigured client or attempted discovery.

Postfix log analysis for security and deliverability

Postfix logs are not just for deliverability. They can reveal authentication failures, relay abuse attempts, rejected senders, bounced recipients, and suspicious outbound patterns. A queue ID links related events across multiple lines, making raw review difficult without structured parsing.

Useful Postfix questions include: which recipient domains rejected the most messages, which senders generated bounces, which queue IDs failed, which relay returned the error, and whether the failure mentions SPF, DKIM, DMARC, TLS, DNS, mailbox quota, or authentication.

For security teams, repeated SASL authentication failures or relay-denied messages may indicate abuse attempts. For operations teams, repeated bounces to a customer domain may require DNS or reputation review.

Dovecot login failure analysis

Dovecot logs show IMAP and POP3 authentication events. These logs are important for mail security because compromised mailboxes can lead to spam, data exposure, and reputation problems. Dovecot events may include failed logins, successful logins, disconnected sessions, TLS details, usernames, remote IPs, and protocols.

When analyzing Dovecot logs, group events by username, source IP, protocol, and result. Look for repeated failed logins against the same mailbox, successful login after repeated failures, login attempts from unexpected locations, and repeated failures across many accounts from one IP.

Correlating auth, firewall and mail logs

The strongest security analysis often combines multiple log types. An IP that triggers SSH failures, firewall denies, and web scanner paths is more suspicious than an IP seen once. A mailbox with Dovecot failures and Postfix sending anomalies may indicate account compromise. A firewall deny spike followed by application errors may show a misconfigured client or automated probe.

AskMyLogs makes this practical by supporting many server log formats in the same analysis flow. Instead of switching between files and tools, teams can ask targeted questions and receive evidence from the parsed events.

Recommended response workflow

1. Identify the top source IPs, usernames, services, ports, and event types.
2. Separate scanner noise from targeted activity using usernames, success events, and repetition.
3. Inspect the raw lines behind the highest-risk pattern.
4. Block or rate-limit obvious abusive IPs when appropriate.
5. Reset credentials and review successful logins when a real account was targeted.
6. Document timestamps, source IPs, usernames, and raw evidence in an incident report.

Conclusion

Security log analysis is most effective when it turns noisy files into structured evidence. SSH auth logs, firewall blocks, Postfix bounces, and Dovecot login failures all contain valuable signals, but the signals only become useful when they can be grouped, counted, searched, and explained. AskMyLogs helps teams move from raw server logs to clear security answers without losing the original evidence.