Bandit Security Scanner Skill

Bandit is a security linter designed to find common security issues in Python code. It processes each file, builds an AST, and runs appropriate plugins against the AST nodes.

When to Use This Skill

Use this skill when:

•Scanning Python code for security vulnerabilities
•Auditing Python projects for hardcoded secrets or credentials
•Detecting dangerous function calls (eval, exec, pickle)
•Finding SQL injection or command injection vulnerabilities
•Checking for weak cryptographic practices
•Reviewing Python packages for malicious patterns
•Performing security code review on Python applications

Decision Tree: Choosing the Right Tool

code

What are you scanning?
│
├── Python source code (.py files)?
│   ├── Own code security audit → bandit -r /path (THIS SKILL)
│   ├── Untrusted/malicious Python → bandit + graudit -d exec,secrets
│   └── Django/Flask app → bandit -r . -t B201,B701,B703,B610,B611
│
├── Python dependencies (requirements.txt)?
│   └── Use guarddog instead: guarddog pypi verify requirements.txt
│
├── Mixed languages or non-Python?
│   └── Use graudit instead (multi-language support)
│
└── Shell scripts?
    └── Use shellcheck instead

Malicious Code Detection Priority

When scanning for potentially malicious or compromised Python code, prioritize these test IDs:

Critical - Immediate Red Flags

Test ID	Detection	Why It's Dangerous
B102	`exec()` usage	Arbitrary code execution
B307	`eval()` usage	Arbitrary code execution
B602	`subprocess(shell=True)`	Reverse shells, command injection
B605	`os.system()`	Command injection
B301	`pickle.load()`	Code execution via deserialization

High - Data Exfiltration & Backdoors

Test ID	Detection	MITRE ATT&CK
B310	`urllib.urlopen`	T1071 - C2 communication
B312	`telnetlib`	T1071 - Unencrypted backdoor
B321	`ftplib`	T1071 - Data exfiltration
B105-B107	Hardcoded passwords	T1552.001 - Embedded credentials
B506	`yaml.load()`	T1059 - Deserialization attack

Recommended Command for Malicious Code Triage

bash

# Critical patterns first (< 30 seconds)
bandit -r . -t B102,B307,B602,B605,B301 -lll --format json

# Full malicious scan with context
bandit -r . -t B102,B105,B106,B107,B301,B307,B310,B312,B321,B506,B602,B605,B608 -f json -o malicious-scan.json

Prerequisites

Install Bandit using pip:

bash

# Install via pip
pip install bandit

# Or with TOML support for pyproject.toml configuration
pip install bandit[toml]

# Verify installation
bandit --version

Core Commands

Basic Scanning

bash

# Scan a single file
bandit target_file.py

# Scan a directory recursively
bandit -r /path/to/project

# Scan with specific severity level (LOW, MEDIUM, HIGH)
bandit -r . -ll  # Only MEDIUM and above
bandit -r . -lll # Only HIGH severity

# Scan with specific confidence level
bandit -r . -ii  # MEDIUM confidence and above
bandit -r . -iii # Only HIGH confidence

Output Formats

bash

# JSON output (recommended for parsing)
bandit -r . -f json -o bandit-results.json

# SARIF output (for IDE integration)
bandit -r . -f sarif -o bandit-results.sarif

# HTML report
bandit -r . -f html -o bandit-report.html

# CSV output
bandit -r . -f csv -o bandit-results.csv

# Custom format with line numbers
bandit -r . -f custom --msg-template "{relpath}:{line}: {test_id}[{severity}]: {msg}"

Selective Scanning

bash

# Run only specific tests
bandit -r . -t B101,B102,B103

# Skip specific tests
bandit -r . -s B101,B601

# Scan specific file patterns
bandit -r . --include "*.py"
bandit -r . --exclude "*/tests/*,*/venv/*"

Configuration File

bash

# Generate sample config
bandit-config-generator -o .bandit

# Use configuration file
bandit -r . -c .bandit

# Use pyproject.toml
bandit -r . -c pyproject.toml

Available Rules/Checks

Dangerous Function Calls

Test ID	Description	Severity	MITRE ATT&CK
B101	assert used	LOW	-
B102	exec used	MEDIUM	T1059 (Command Execution)
B103	set_bad_file_permissions	MEDIUM	T1222 (File Permission Modification)
B104	hardcoded_bind_all_interfaces	MEDIUM	T1071 (Application Layer Protocol)
B105	hardcoded_password_string	LOW	T1552.001 (Credentials in Files)
B106	hardcoded_password_funcarg	LOW	T1552.001 (Credentials in Files)
B107	hardcoded_password_default	LOW	T1552.001 (Credentials in Files)
B108	hardcoded_tmp_directory	MEDIUM	T1074 (Data Staged)
B110	try_except_pass	LOW	-
B112	try_except_continue	LOW	-

Injection Vulnerabilities

Test ID	Description	Severity	MITRE ATT&CK
B201	flask_debug_true	HIGH	T1190 (Exploit Public-Facing Application)
B301	pickle	MEDIUM	T1059 (Deserialization)
B302	marshal	MEDIUM	T1059 (Deserialization)
B303	md5/sha1	MEDIUM	T1600 (Weaken Encryption)
B304	insecure_cipher	HIGH	T1600 (Weaken Encryption)
B305	insecure_cipher_mode	MEDIUM	T1600 (Weaken Encryption)
B306	mktemp_q	MEDIUM	T1074 (Data Staged)
B307	eval	MEDIUM	T1059 (Command Execution)
B308	mark_safe	MEDIUM	T1059.007 (JavaScript)
B310	urllib_urlopen	MEDIUM	T1071 (Application Layer Protocol)
B311	random	LOW	T1600 (Weaken Encryption)
B312	telnetlib	HIGH	T1071 (Application Layer Protocol)
B313-B320	xml vulnerabilities	MEDIUM	T1059 (XXE)
B321	ftplib	HIGH	T1071 (Application Layer Protocol)
B323	unverified_context	MEDIUM	T1557 (MITM)
B324	hashlib_insecure	MEDIUM	T1600 (Weaken Encryption)

Shell Injection

Test ID	Description	Severity	MITRE ATT&CK
B601	paramiko_calls	MEDIUM	T1021.004 (SSH)
B602	subprocess_popen_shell	HIGH	T1059.004 (Unix Shell)
B603	subprocess_without_shell	LOW	T1059 (Command Execution)
B604	any_other_function_shell	MEDIUM	T1059.004 (Unix Shell)
B605	start_process_shell	HIGH	T1059.004 (Unix Shell)
B606	start_process_no_shell	LOW	T1059 (Command Execution)
B607	start_process_partial_path	LOW	T1059 (Command Execution)
B608	hardcoded_sql_expressions	MEDIUM	T1190 (SQL Injection)
B609	linux_commands_wildcard	HIGH	T1059.004 (Unix Shell)
B610	django_extra_used	MEDIUM	T1190 (SQL Injection)
B611	django_rawsql_used	MEDIUM	T1190 (SQL Injection)

Cryptographic Issues

Test ID	Description	Severity	MITRE ATT&CK
B501	request_with_no_cert_validation	HIGH	T1557 (MITM)
B502	ssl_with_bad_version	HIGH	T1600 (Weaken Encryption)
B503	ssl_with_bad_defaults	MEDIUM	T1600 (Weaken Encryption)
B504	ssl_with_no_version	MEDIUM	T1600 (Weaken Encryption)
B505	weak_cryptographic_key	HIGH	T1600 (Weaken Encryption)
B506	yaml_load	MEDIUM	T1059 (Deserialization)
B507	ssh_no_host_key_verification	HIGH	T1557 (MITM)
B508	snmp_insecure_version	MEDIUM	T1071 (Application Layer Protocol)
B509	snmp_weak_cryptography	MEDIUM	T1600 (Weaken Encryption)

Network Security

Test ID	Description	Severity	MITRE ATT&CK
B701	jinja2_autoescape_false	HIGH	T1059.007 (XSS)
B702	use_of_mako_templates	MEDIUM	T1059.007 (XSS)
B703	django_mark_safe	MEDIUM	T1059.007 (XSS)

Recommended Scanning Workflows

Quick Triage (< 30 seconds)

For rapid assessment of unknown or suspicious Python code:

bash

# Check for obvious malicious patterns only
bandit -r . -t B102,B307,B602,B605 -lll

Standard Security Audit (1-2 minutes)

For routine code review:

bash

# Step 1: High-severity issues
bandit -r . -lll -f json -o high-severity.json

# Step 2: Medium and above with exclusions
bandit -r . -ll --exclude "*/tests/*,*/venv/*"

Deep Malicious Code Scan (5-10 minutes)

For untrusted code or incident response:

bash

# Comprehensive scan with all context
bandit -r . -f json -o full-scan.json

# Then combine with graudit for non-Python embedded code
graudit -d exec . && graudit -d secrets .

Baseline Workflow

For tracking security improvements over time:

bash

# Create baseline for existing code
bandit -r . -f json -o baseline.json

# Later scans compare against baseline
bandit -r . -b baseline.json

CI/CD Integration

bash

# Fail pipeline on HIGH severity with HIGH confidence
bandit -r . -lll -iii || exit 1

# Don't fail on findings (reporting only)
bandit -r . -ll --exit-zero

# Fail on MEDIUM+ findings
bandit -r . -ll

Framework-Specific Scanning

Django Applications

bash

bandit -r . -t B201,B608,B610,B611,B701,B703 -f json
# Checks: Debug mode, SQL injection, XSS via mark_safe, raw SQL

Flask Applications

bash

bandit -r . -t B104,B201,B310,B701 -f json
# Checks: Debug mode, bind all interfaces, Jinja2 XSS

Data Processing / ML Pipelines

bash

bandit -r . -t B301,B302,B506 -f json
# Checks: pickle, marshal, yaml deserialization

API Services

bash

bandit -r . -t B105,B106,B107,B501,B502,B503 -f json
# Checks: Hardcoded creds, SSL/TLS issues

Interpreting Results

Severity Levels

•HIGH: Critical security issues requiring immediate attention
•MEDIUM: Significant issues that should be addressed
•LOW: Minor issues or potential concerns

Confidence Levels

•HIGH: Very confident this is a real issue
•MEDIUM: Likely an issue but may need verification
•LOW: Possible issue, manual review recommended

Example Output

code

>> Issue: [B102:exec_used] Use of exec detected.
   Severity: Medium   Confidence: High
   CWE: CWE-78 (https://cwe.mitre.org/data/definitions/78.html)
   Location: ./malicious.py:15:0
   More Info: https://bandit.readthedocs.io/en/latest/plugins/b102_exec_used.html

Verifying Findings

For each Bandit finding, verify:

• Is user/external input involved? (not hardcoded safe values)
• Can an attacker control the input path?
• Is there sanitization/validation before the dangerous call?
• Is this production code? (not tests/examples/documentation)
• Does the confidence level match manual assessment?

Common False Positives

Test ID	False Positive Scenario	Recommendation
B101	`assert` in test files	Skip with `--exclude "/tests/"`
B311	`random` used for non-security purposes (UI, games)	Skip with `-s B311` if confirmed safe
B105	Variables named `password` that aren't credentials	Manual review, consider renaming
B602	`subprocess(shell=True)` with hardcoded commands	Verify no user input reaches command
B108	`/tmp` usage in containerized environments	Context-dependent, may be acceptable

Integration with Other Security Tools

For comprehensive security analysis, combine Bandit with other skills:

Code Type	Primary Tool	Secondary Scan
Python source (.py)	Bandit (this skill)	graudit -d secrets
Python packages	guarddog	Extract then Bandit
Mixed Python + Shell	Bandit + ShellCheck	graudit -d exec
Django/Flask + JS	Bandit	graudit -d js,xss

Recommended Multi-Tool Workflow

bash

# 1. Python-specific deep analysis
bandit -r . -f json -o bandit-results.json

# 2. Secrets scan (catches patterns Bandit might miss)
graudit -d secrets .

# 3. Dependency audit
guarddog pypi verify requirements.txt

Additional Resources

•Malicious Patterns Reference - Educational examples of dangerous code patterns that Bandit detects, including exec(), eval(), pickle, shell injection, SQL injection, and hardcoded credentials. Use this reference to understand detection capabilities and educate developers about secure coding.

Limitations

•Static Analysis Only: Cannot detect runtime vulnerabilities or dynamic code execution patterns
•Python Only: Does not scan other languages in polyglot projects
•AST-Based: May miss vulnerabilities in string-constructed code
•False Positives: Some patterns (like random for non-security uses) may trigger warnings
•No Data Flow: Limited taint tracking compared to commercial SAST tools
•Configuration Required: May need tuning to reduce noise in large codebases
•No Dependency Scanning: Does not check for vulnerable dependencies (use pip-audit or safety for that)