threat-hunting

Threat Hunting & Detection

When to Activate

• Proactive threat hunting across infrastructure
• Correlating security events across multiple sources
• Detecting anomalous behavior patterns
• Mapping attacks to MITRE ATT&CK framework
• Writing detection rules (Sigma, YARA, Snort)
• Incident response triage

MITRE ATT&CK Mapping

Common Techniques to Hunt

| Tactic | Technique | Detection Focus | |--------|-----------|----------------| | Initial Access | Phishing, Exploit Public-Facing App | Email gateways, web WAF logs | | Execution | PowerShell, WMI, Scheduled Tasks | PS logs, Sysmon Event ID 1 | | Persistence | Registry Run Keys, Scheduled Tasks | Registry monitoring, task scheduler logs | | Privilege Escalation | Token Manipulation, Exploitation | Access token changes, exploit indicators | | Defense Evasion | Obfuscated Files, Indicator Removal | File entropy analysis, log gap detection | | Credential Access | LSASS Memory, OS Credential Dumping | LSASS access patterns, dump file creation | | Discovery | Network Share Discovery, System Info Discovery | Net commands, systeminfo execution | | Lateral Movement | SMB/Windows Admin Shares, WMI | SMB connection patterns, remote WMI calls | | Collection | Data Staged, Archive Collected Data | Unusual archive operations, staging directories | | Exfiltration | Exfiltration Over C2, DNS | DNS query volume anomalies, C2 beacon patterns |

Log Analysis & Correlation

Key Event Sources

# Windows (Sysmon)
Event ID 1: Process creation
Event ID 3: Network connection
Event ID 7: Image loaded
Event ID 11: File creation
Event ID 12: Registry object added/modified
Event ID 13: Registry value set
Event ID 15: File creation stream hash
Event ID 17: Pipe created
Event ID 22: DNS query
Event ID 25: Process tampering

# Linux (auditd)
type=EXECVE: Command execution
type=CONNECT: Network connections
type=PATH: File access
type=SYSCALL: System calls (esp. ptrace, execve)

# Network (Zeek/Suricata)
DNS queries and responses
HTTP requests and responses
SSL/TLS certificate analysis
File extraction and hashing

Correlation Queries

-- Splunk: PowerShell encoded command
index=security EventCode=4688 
| where match(Process_Command_Line, "powershell.*-enc") 
| stats count by Computer, User, _time
| where count > 3

-- Splunk: Lateral movement via PsExec
index=security EventCode=7045 Service_Name="PSEXESVC"
| stats count by Computer, User
| where count > 1

-- Sigma equivalent
detection:
    selection:
        EventID: 4688
        CommandLine|contains|all:
            - 'powershell'
            - '-enc'
            - '-encodedcommand'
    condition: selection

Behavioral Anomaly Detection

Baselines

# Normal user behavior:
- Login times and duration
- Common processes and commands
- Network destinations and volumes
- File access patterns

# Anomaly indicators:
- Processes running at unusual hours
- New network destinations (never before seen)
- Sudden increase in data access volume
- Commands that deviate from user's normal pattern
- Service installations on workstations

Hunting Hypotheses

# Generate and test hunting hypotheses:
1. "If there's credential dumping, we'll see Mimikatz or similar tool execution"
2. "If lateral movement occurs, we'll see new admin share connections"
3. "If data exfiltration happens, we'll see unusual outbound DNS or HTTPS traffic"
4. "If there's persistence, we'll see new scheduled tasks or registry modifications"

# Validate with:
- Historical log analysis (last 30-90 days)
- Endpoint telemetry (processes, network, files)
- Network flow data (NetFlow, PCAP)
- Cloud audit logs (CloudTrail, Azure Activity Log)

Detection Rule Development

Sigma Rule Template

title: Suspicious PowerShell Execution
id: rule-uuid-here
status: experimental
description: Detects PowerShell execution with encoded commands and download cradles
references:
    - https://attack.mitre.org/techniques/T1059/001/
author: analyst
date: 2026/05/19
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        Image|endswith: '\powershell.exe'
    encoded:
        CommandLine|contains:
            - '-enc'
            - '-encodedcommand'
    download:
        CommandLine|contains:
            - 'DownloadString'
            - 'DownloadFile'
            - 'IEX'
            - 'Invoke-Expression'
    condition: selection and (encoded or download)
falsepositives:
    - Legitimate IT automation scripts
    - Software deployment tools
level: high
tags:
    - attack.execution
    - attack.t1059.001

YARA Network Detection

rule C2_Beacon_Pattern {
    meta:
        description = "Detects C2 beacon traffic patterns"
    strings:
        $beacon_http = /POST \/gate\.php HTTP\/1\.1\r\nHost: [^\r\n]+\r\nUser-Agent: Mozilla\/[\d.]+/
        $beacon_dns = /[a-z0-9]{32,}\.attacker-domain\.(com|net|org)/
    condition:
        $beacon_http or $beacon_dns
}

Advanced: KQL/SPL Hunting Queries

Splunk (SPL) Advanced Queries

| Detect credential dumping (LSASS access)
index=sysmon EventCode=10 TargetImage="*lsass.exe"
| where NOT match(SourceImage, "(?i)(csrss|services|svchost|wininit|MsMpEng|CrowdStrike)")
| stats count values(SourceImage) as tools by Computer
| where count > 0

| Detect DCSync (Directory Replication)
index=security EventCode=4662 
| where match(Properties, "(?i)(1131f6aa|1131f6ad|89e95b76)")
| where NOT match(SubjectUserName, "(?i)(\\$|MSOL_)")
| stats count by SubjectUserName, ObjectName

| Detect Kerberoasting
index=security EventCode=4769 TicketEncryptionType=0x17 ServiceName!="krbtgt" ServiceName!="*$"
| stats count dc(ServiceName) as unique_spns by IpAddress, TargetUserName
| where unique_spns > 3

| Detect lateral movement (remote service creation)
index=security EventCode=7045
| where NOT match(Service_File_Name, "(?i)(windows|program files|syswow64)")
| stats count values(Service_File_Name) as services by Computer, SubjectUserName

| Detect pass-the-hash (NTLM type 3 with no type 1/2)
index=security EventCode=4624 LogonType=3 AuthenticationPackageName=NTLM
| where LmPackageName="NTLM V2" AND TargetUserName!="ANONYMOUS LOGON"
| stats count by SourceNetworkAddress, TargetUserName, WorkstationName
| where count > 5

| Detect process injection (Sysmon CreateRemoteThread)
index=sysmon EventCode=8
| where SourceImage!=TargetImage
| where NOT match(SourceImage, "(?i)(csrss|lsass|services|svchost)")
| stats count values(TargetImage) as targets by SourceImage, Computer

KQL (Microsoft Sentinel / Defender)

// Detect encoded PowerShell execution
DeviceProcessEvents
| where FileName =~ "powershell.exe"
| where ProcessCommandLine has_any ("-enc", "-encodedcommand", "frombase64")
| where ProcessCommandLine !has "Microsoft" // exclude legit
| project Timestamp, DeviceName, AccountName, ProcessCommandLine
| summarize count() by DeviceName, AccountName, bin(Timestamp, 1h)
| where count_ > 3

// Detect LSASS credential access
DeviceProcessEvents
| where FileName =~ "lsass.exe"
| join kind=inner (
    DeviceFileEvents | where ActionType == "FileCreated" | where FileName endswith ".dmp"
) on DeviceId
| project Timestamp, DeviceName, InitiatingProcessFileName

// Detect suspicious named pipe creation (C2 indicators)
DeviceEvents
| where ActionType == "NamedPipeEvent"
| where AdditionalFields has_any ("\\msagent_", "\\MSSE-", "\\postex_", "\\status_")
| summarize count() by DeviceName, PipeName=tostring(parse_json(AdditionalFields).PipeName)

// Detect Kerberos ticket anomalies (Golden/Silver ticket)
IdentityQueryEvents
| where ActionType == "LDAP query"
| where QueryTarget has "krbtgt"
| join kind=inner (
    IdentityLogonEvents | where LogonType == "Kerberos"
    | where isempty(AccountDomain) or AccountDomain != DeviceName
) on AccountName
| project Timestamp, AccountName, DeviceName, QueryTarget

// Hunt for living-off-the-land binaries (LOLBins)
let lolbins = dynamic(["certutil.exe",