Threat Detection and Network Defense
Study Cisco CCST Cybersecurity threat detection: logs, SIEM, IDS, IPS, DNS, firewall, email, endpoint alerts, and network defense evidence.
Threat Detection and Network Defense questions test whether you can read basic evidence without overclaiming. An alert is a signal, not automatically a confirmed incident.
Evidence sources
| Source |
What it can show |
| Firewall log |
allowed or denied traffic, source, destination, port, rule |
| DNS log |
queried domains, response, host, frequency |
| Web proxy |
URL, category, user, action, downloads |
| Email security |
sender, headers, attachment, URL, authentication result |
| Endpoint alert |
host, user, process, file, hash, action taken |
| IDS/IPS |
signature, direction, packet clue, action |
| SIEM |
correlated events and timeline across systems |
Alert triage sequence
flowchart TD
A["Alert"] --> V["Validate source and asset"]
V --> T["Build timeline"]
T --> C["Correlate logs"]
C --> S["Determine scope"]
S --> N["Choose next action"]
Common threat cues
| Cue |
Possible issue |
| unusual outbound DNS queries |
malware, command-and-control, tunneling, or misconfiguration |
| many failed logins then success |
password attack or compromised account |
| unexpected process spawning script interpreter |
malware, living-off-the-land activity, or admin script |
| large outbound transfer |
data exfiltration or legitimate backup |
| user clicks suspicious email link |
phishing investigation |
| IDS signature on exposed server |
possible exploit attempt needing validation |
Network defense control matching
| Need |
Likely control |
| block known malicious domain |
DNS filtering or proxy control |
| stop unwanted inbound traffic |
firewall rule or ACL |
| observe suspicious traffic |
IDS, logs, packet capture, SIEM |
| block known exploit traffic |
IPS where appropriate |
| reduce lateral movement |
segmentation and least privilege |
| protect users from phishing links |
email security, browser/proxy controls, reporting workflow |
Exam traps to avoid
- Do not declare compromise from one log line without context.
- Do not ignore direction: inbound scan, outbound beacon, and internal lateral movement are different.
- Do not choose packet capture when a simple log or alert already answers the question.
- Do not confuse IDS detection with IPS blocking.
Revised on Monday, June 15, 2026