Performing Insider Threat Investigation
When to Use
- DLP (Data Loss Prevention) alerts on large data transfers to personal cloud storage or USB devices
- User behavior analytics (UBA) detects anomalous access patterns for a user account
- HR reports a departing employee suspected of taking proprietary information
- A privileged user is observed accessing systems outside their job function
- Whistleblower or coworker report alleges policy violations or data theft
Do not use for external attacker investigations where compromised credentials are used without insider collusion; use standard incident response procedures instead.
Prerequisites
- Legal counsel approval before initiating any monitoring or investigation of an employee
- HR partnership with defined investigation procedures and employee privacy guidelines
- DLP platform with content inspection and policy enforcement (Symantec DLP, Microsoft Purview, Digital Guardian)
- User behavior analytics platform (Microsoft Sentinel UEBA, Exabeam, Securonix)
- Forensic imaging capability for endpoint examination
- Chain of custody procedures for evidence that may be used in legal proceedings
- Clear authority and scope documentation approved by legal and HR
Workflow
Step 1: Receive and Validate the Allegation
Document the initial report and validate before proceeding:
- Record the source of the allegation (DLP alert, UBA detection, HR referral, manager report)
- Confirm with legal counsel that the investigation is authorized
- Define the investigation scope: what activity is being investigated, time period, systems involved
- Establish the investigation team: security, legal, HR (never investigate alone)
- Create a restricted case file accessible only to the investigation team
Investigation Authorization:
━━━━━━━━━━━━━━━━━━━━━━━━━━━
Case ID: INV-2025-042
Subject: [Employee Name] - [Title] - [Department]
Allegation: Unauthorized transfer of proprietary data to personal cloud storage
Reported By: DLP system alert + manager concern
Legal Approval: [Counsel Name] - 2025-11-15
HR Liaison: [HR Name]
Scope: File access and transfer activity from 2025-10-01 to present
Systems in Scope: Workstation, email, cloud storage, VPN, DLP logs
Step 2: Collect Evidence Covertly
Gather evidence without alerting the subject to the investigation:
Log-Based Evidence (non-intrusive):
- DLP logs: file transfers, policy violations, content matches
- Cloud access logs: SharePoint, OneDrive, Google Drive activity
- Email logs: messages to personal accounts, large attachments, forwarding rules
- VPN and authentication logs: access times, locations, devices
- Badge access logs: physical access patterns
- Print logs: large print jobs of sensitive documents
- USB device connection logs: device type, serial number, connection times
User Activity Monitoring (requires legal approval):
- Screen capture or session recording (only if legally authorized and documented)
- Keystroke logging (jurisdiction-dependent, requires explicit legal approval)
- Network traffic capture for the subject's workstation
Endpoint Forensics (if warranted by evidence):
- Create forensic image of the subject's workstation
- Analyze browser history, download history, and installed applications
- Examine deleted files and Recycle Bin contents
- Review cloud sync application logs (Dropbox, Google Drive desktop client)
Step 3: Analyze User Behavior Patterns
Build a behavioral profile comparing normal vs. anomalous activity:
Behavioral Analysis:
━━━━━━━━━━━━━━━━━━
Normal Baseline (6-month average):
- Login time: 08:30-09:00 weekdays
- Files accessed: 15-25 per day (marketing department files)
- Email volume: 45 sent, 80 received per day
- Data transferred: 50MB per day average
- USB usage: None
Investigation Period (last 30 days):
- Login time: 22:00-02:00 (after hours, multiple occasions)
- Files accessed: 200+ per day (finance, engineering, executive files)
- Email volume: 120 sent per day (30% to personal gmail)
- Data transferred: 2.5GB per day average
- USB usage: 3 unique devices connected (Kingston DataTraveler)
- Print jobs: 847 pages (competitor analysis, customer lists, source code)
Anomaly Score: 94/100 (Critical)
Step 4: Reconstruct the Activity Timeline
Build a chronological timeline of the subject's actions:
Timeline of Activity:
2025-10-15 Subject submits resignation (2-week notice)
2025-10-16 First after-hours login at 23:15, accessed engineering Git repository
2025-10-17 USB device (Kingston DT 64GB) first connected at 23:30
2025-10-18 DLP alert: 450 files copied to USB, including CAD drawings
2025-10-19 200+ emails forwarded to personal Gmail account
2025-10-20 Google Drive desktop client installed, syncing corporate SharePoint
2025-10-22 Accessed executive SharePoint site (not normally accessed)
2025-10-25 Second USB device connected, 2.1GB transferred
2025-10-28 Print job: 847 pages including customer contact database
Step 5: Assess Impact and Determine Response
Evaluate the severity and coordinate the response with HR and legal:
Impact Assessment:
- What data was accessed or exfiltrated (classification level, business impact)
- Was the data shared externally (competitors, public, personal storage)
- Regulatory implications (PII, PHI, financial data, export-controlled)
- Contractual implications (NDA violations, IP assignment agreements)
- Potential financial damage to the organization
Response Options (determined by legal and HR):
- Confront the subject with evidence during an interview (HR-led)
- Terminate employment and revoke all access immediately
- Pursue civil litigation for breach of NDA or trade secret theft
- Refer to law enforcement for criminal prosecution (theft of trade secrets, CFAA violation)
- Negotiate a settlement with return/destruction of data
Step 6: Preserve Evidence for Legal Proceedings
Ensure all evidence meets legal admissibility standards:
- Maintain strict chain of custody for all physical and digital evidence
- Document all analysis steps in detail (reproducible by another examiner)
- Hash all evidence files and maintain an integrity log
- Store evidence in a secure, access-controlled repository with audit logging
- Retain evidence per legal hold requirements (do not destroy during active investigation or litigation)
Key Concepts
| Term |
Definition |
| Insider Threat |
Risk posed by individuals with authorized access who intentionally or unintentionally cause harm to the organization |
| User Behavior Analytics (UBA) |
Technology that analyzes user activity patterns to detect anomalies indicating potential insider threats |
| Data Loss Prevention (DLP) |
Technology that monitors, detects, and blocks unauthorized transfer of sensitive data outside the organization |
| Legal Hold |
Directive to preserve all relevant evidence and suspend normal document destruction policies during an investigation |
| Need to Know |
Information access principle restricting insider threat investigation details to only authorized team members |
| Exfiltration Vector |
Method used to move data outside the organization: USB, email, cloud storage, print, screen capture, photography |
Tools & Systems
- Microsoft Purview (formerly Compliance Center): Insider risk management, DLP, eDiscovery, and content search
- Exabeam / Securonix: User and entity behavior analytics (UEBA) platforms for anomaly detection
- Digital Guardian: DLP and insider threat detection platform with endpoint agent
- Magnet AXIOM: Digital forensics platform supporting endpoint, cloud, and mobile evidence analysis
- Relativity: eDiscovery platform for legal review of collected evidence in insider threat cases
Common Scenarios
Scenario: Departing Engineer Exfiltrating Source Code
Context: A senior software engineer with access to critical repositories submits a two-week resignation notice. The engineering manager reports that the engineer has been working unusual hours and downloading large amounts of code.
Approach:
- Obtain legal authorization to investigate before taking any action
- Pull Git access logs showing repository clones and downloads for the past 60 days
- Review DLP logs for USB device connections and large file transfers
- Check email gateway for messages with code attachments sent to personal accounts
- Analyze browser history for personal cloud storage uploads
- Image the workstation forensically before the employee's last day
- Present findings to legal and HR for determination of next steps
Pitfalls:
- Investigating without legal counsel authorization (may violate employee privacy rights)
- Alerting the subject to the investigation before evidence is preserved
- Not preserving the workstation before the employee's departure date
- Assuming all after-hours access is malicious without comparing to the employee's historical baseline
- Failing to check personal mobile devices that may have accessed corporate cloud services
Output Format
INSIDER THREAT INVESTIGATION REPORT
=====================================
Case ID: INV-2025-042
Classification: CONFIDENTIAL - Need to Know Only
Subject: [Name Redacted] - Senior Engineer
Investigation Period: 2025-10-01 to 2025-10-28
Investigator: [Name]
Legal Counsel: [Name]
HR Liaison: [Name]
ALLEGATION
Unauthorized exfiltration of proprietary source code and customer
data following resignation submission.
EVIDENCE SUMMARY
1. Git logs: 47 repositories cloned (vs. baseline of 3)
2. USB transfers: 4.6 GB across 3 unique devices over 12 sessions
3. Email: 200+ emails with attachments forwarded to personal Gmail
4. Cloud: Google Drive sync client installed, syncing corporate files
5. Print: 847 pages including customer contact database
6. Physical access: After-hours badge access on 8 of 12 workdays
BEHAVIORAL ANALYSIS
[Baseline vs. anomalous activity comparison]
IMPACT ASSESSMENT
Data Classification: Confidential (source code, customer PII)
Estimated Volume: 7.2 GB exfiltrated
Regulatory Impact: Potential GDPR notification (customer PII)
Business Impact: Competitive advantage at risk
TIMELINE
[Chronological event listing]
RECOMMENDATIONS
1. [Legal/HR decision on employment action]
2. [Evidence preservation actions]
3. [Regulatory notification assessment]
4. [Access control improvements]
Source: mukul975/Anthropic-Cybersecurity-Skills → skills/performing-insider-threat-investigation/SKILL.md
1---2name: performing-insider-threat-investigation3description: 'Investigates insider threat incidents involving employees, contractors, or trusted partners who misuse authorized access to steal data, sabotage systems, or violate security policies. Combines digital forensics, user behavior analytics, and HR/legal coordination to build an evidence-based case. Activates for requests involving insider threat investigation, employee data theft, privilege misuse, user behavior anomaly, or internal threat detection. '4---5
6
7# Performing Insider Threat Investigation
8
9## When to Use
10
11- DLP (Data Loss Prevention) alerts on large data transfers to personal cloud storage or USB devices
12- User behavior analytics (UBA) detects anomalous access patterns for a user account
13- HR reports a departing employee suspected of taking proprietary information
14- A privileged user is observed accessing systems outside their job function
15- Whistleblower or coworker report alleges policy violations or data theft
16
17**Do not use** for external attacker investigations where compromised credentials are used without insider collusion; use standard incident response procedures instead.
18
19## Prerequisites
20
21- Legal counsel approval before initiating any monitoring or investigation of an employee
22- HR partnership with defined investigation procedures and employee privacy guidelines
23- DLP platform with content inspection and policy enforcement (Symantec DLP, Microsoft Purview, Digital Guardian)
24- User behavior analytics platform (Microsoft Sentinel UEBA, Exabeam, Securonix)
25- Forensic imaging capability for endpoint examination
26- Chain of custody procedures for evidence that may be used in legal proceedings
27- Clear authority and scope documentation approved by legal and HR
28
29## Workflow
30
31### Step 1: Receive and Validate the Allegation
32
33Document the initial report and validate before proceeding:
34
35- Record the source of the allegation (DLP alert, UBA detection, HR referral, manager report)
36- Confirm with legal counsel that the investigation is authorized
37- Define the investigation scope: what activity is being investigated, time period, systems involved
38- Establish the investigation team: security, legal, HR (never investigate alone)
39- Create a restricted case file accessible only to the investigation team
40
41```
42Investigation Authorization:
43━━━━━━━━━━━━━━━━━━━━━━━━━━━
44Case ID: INV-2025-042
45Subject: [Employee Name] - [Title] - [Department]
46Allegation: Unauthorized transfer of proprietary data to personal cloud storage
47Reported By: DLP system alert + manager concern
48Legal Approval: [Counsel Name] - 2025-11-15
49HR Liaison: [HR Name]
50Scope: File access and transfer activity from 2025-10-01 to present
51Systems in Scope: Workstation, email, cloud storage, VPN, DLP logs
52```
53
54### Step 2: Collect Evidence Covertly
55
56Gather evidence without alerting the subject to the investigation:
57
58**Log-Based Evidence (non-intrusive):**
59- DLP logs: file transfers, policy violations, content matches
60- Cloud access logs: SharePoint, OneDrive, Google Drive activity
61- Email logs: messages to personal accounts, large attachments, forwarding rules
62- VPN and authentication logs: access times, locations, devices
63- Badge access logs: physical access patterns
64- Print logs: large print jobs of sensitive documents
65- USB device connection logs: device type, serial number, connection times
66
67**User Activity Monitoring (requires legal approval):**
68- Screen capture or session recording (only if legally authorized and documented)
69- Keystroke logging (jurisdiction-dependent, requires explicit legal approval)
70- Network traffic capture for the subject's workstation
71
72**Endpoint Forensics (if warranted by evidence):**
73- Create forensic image of the subject's workstation
74- Analyze browser history, download history, and installed applications
75- Examine deleted files and Recycle Bin contents
76- Review cloud sync application logs (Dropbox, Google Drive desktop client)
77
78### Step 3: Analyze User Behavior Patterns
79
80Build a behavioral profile comparing normal vs. anomalous activity:
81
82```
83Behavioral Analysis:
84━━━━━━━━━━━━━━━━━━
85Normal Baseline (6-month average):
86- Login time: 08:30-09:00 weekdays
87- Files accessed: 15-25 per day (marketing department files)
88- Email volume: 45 sent, 80 received per day
89- Data transferred: 50MB per day average
90- USB usage: None
91
92Investigation Period (last 30 days):
93- Login time: 22:00-02:00 (after hours, multiple occasions)
94- Files accessed: 200+ per day (finance, engineering, executive files)
95- Email volume: 120 sent per day (30% to personal gmail)
96- Data transferred: 2.5GB per day average
97- USB usage: 3 unique devices connected (Kingston DataTraveler)
98- Print jobs: 847 pages (competitor analysis, customer lists, source code)
99
100Anomaly Score: 94/100 (Critical)
101```
102
103### Step 4: Reconstruct the Activity Timeline
104
105Build a chronological timeline of the subject's actions:
106
107```
108Timeline of Activity:
1092025-10-15 Subject submits resignation (2-week notice)
1102025-10-16 First after-hours login at 23:15, accessed engineering Git repository
1112025-10-17 USB device (Kingston DT 64GB) first connected at 23:30
1122025-10-18 DLP alert: 450 files copied to USB, including CAD drawings
1132025-10-19 200+ emails forwarded to personal Gmail account
1142025-10-20 Google Drive desktop client installed, syncing corporate SharePoint
1152025-10-22 Accessed executive SharePoint site (not normally accessed)
1162025-10-25 Second USB device connected, 2.1GB transferred
1172025-10-28 Print job: 847 pages including customer contact database
118```
119
120### Step 5: Assess Impact and Determine Response
121
122Evaluate the severity and coordinate the response with HR and legal:
123
124**Impact Assessment:**
125- What data was accessed or exfiltrated (classification level, business impact)
126- Was the data shared externally (competitors, public, personal storage)
127- Regulatory implications (PII, PHI, financial data, export-controlled)
128- Contractual implications (NDA violations, IP assignment agreements)
129- Potential financial damage to the organization
130
131**Response Options (determined by legal and HR):**
132- Confront the subject with evidence during an interview (HR-led)
133- Terminate employment and revoke all access immediately
134- Pursue civil litigation for breach of NDA or trade secret theft
135- Refer to law enforcement for criminal prosecution (theft of trade secrets, CFAA violation)
136- Negotiate a settlement with return/destruction of data
137
138### Step 6: Preserve Evidence for Legal Proceedings
139
140Ensure all evidence meets legal admissibility standards:
141
142- Maintain strict chain of custody for all physical and digital evidence
143- Document all analysis steps in detail (reproducible by another examiner)
144- Hash all evidence files and maintain an integrity log
145- Store evidence in a secure, access-controlled repository with audit logging
146- Retain evidence per legal hold requirements (do not destroy during active investigation or litigation)
147
148## Key Concepts
149
150| Term | Definition |
151|------|------------|
152| **Insider Threat** | Risk posed by individuals with authorized access who intentionally or unintentionally cause harm to the organization |
153| **User Behavior Analytics (UBA)** | Technology that analyzes user activity patterns to detect anomalies indicating potential insider threats |
154| **Data Loss Prevention (DLP)** | Technology that monitors, detects, and blocks unauthorized transfer of sensitive data outside the organization |
155| **Legal Hold** | Directive to preserve all relevant evidence and suspend normal document destruction policies during an investigation |
156| **Need to Know** | Information access principle restricting insider threat investigation details to only authorized team members |
157| **Exfiltration Vector** | Method used to move data outside the organization: USB, email, cloud storage, print, screen capture, photography |
158
159## Tools & Systems
160
161- **Microsoft Purview (formerly Compliance Center)**: Insider risk management, DLP, eDiscovery, and content search
162- **Exabeam / Securonix**: User and entity behavior analytics (UEBA) platforms for anomaly detection
163- **Digital Guardian**: DLP and insider threat detection platform with endpoint agent
164- **Magnet AXIOM**: Digital forensics platform supporting endpoint, cloud, and mobile evidence analysis
165- **Relativity**: eDiscovery platform for legal review of collected evidence in insider threat cases
166
167## Common Scenarios
168
169### Scenario: Departing Engineer Exfiltrating Source Code
170
171**Context**: A senior software engineer with access to critical repositories submits a two-week resignation notice. The engineering manager reports that the engineer has been working unusual hours and downloading large amounts of code.
172
173**Approach**:
1741. Obtain legal authorization to investigate before taking any action
1752. Pull Git access logs showing repository clones and downloads for the past 60 days
1763. Review DLP logs for USB device connections and large file transfers
1774. Check email gateway for messages with code attachments sent to personal accounts
1785. Analyze browser history for personal cloud storage uploads
1796. Image the workstation forensically before the employee's last day
1807. Present findings to legal and HR for determination of next steps
181
182**Pitfalls**:
183- Investigating without legal counsel authorization (may violate employee privacy rights)
184- Alerting the subject to the investigation before evidence is preserved
185- Not preserving the workstation before the employee's departure date
186- Assuming all after-hours access is malicious without comparing to the employee's historical baseline
187- Failing to check personal mobile devices that may have accessed corporate cloud services
188
189## Output Format
190
191```
192INSIDER THREAT INVESTIGATION REPORT
193=====================================
194Case ID: INV-2025-042
195Classification: CONFIDENTIAL - Need to Know Only
196Subject: [Name Redacted] - Senior Engineer
197Investigation Period: 2025-10-01 to 2025-10-28
198Investigator: [Name]
199Legal Counsel: [Name]
200HR Liaison: [Name]
201
202ALLEGATION
203Unauthorized exfiltration of proprietary source code and customer
204data following resignation submission.
205
206EVIDENCE SUMMARY
2071. Git logs: 47 repositories cloned (vs. baseline of 3)
2082. USB transfers: 4.6 GB across 3 unique devices over 12 sessions
2093. Email: 200+ emails with attachments forwarded to personal Gmail
2104. Cloud: Google Drive sync client installed, syncing corporate files
2115. Print: 847 pages including customer contact database
2126. Physical access: After-hours badge access on 8 of 12 workdays
213
214BEHAVIORAL ANALYSIS
215[Baseline vs. anomalous activity comparison]
216
217IMPACT ASSESSMENT
218Data Classification: Confidential (source code, customer PII)
219Estimated Volume: 7.2 GB exfiltrated
220Regulatory Impact: Potential GDPR notification (customer PII)
221Business Impact: Competitive advantage at risk
222
223TIMELINE
224[Chronological event listing]
225
226RECOMMENDATIONS
2271. [Legal/HR decision on employment action]
2282. [Evidence preservation actions]
2293. [Regulatory notification assessment]
2304. [Access control improvements]
231```
232
233---
234
235**Source:** [`mukul975/Anthropic-Cybersecurity-Skills`](https://github.com/mukul975/Anthropic-Cybersecurity-Skills) → `skills/performing-insider-threat-investigation/SKILL.md`
thedixitjain