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Introduction to

Cybersecurity

David J. Malan

malan@harvard.edu

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Souvenir Photo

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Introduction to

Cybersecurity

David J. Malan

malan@harvard.edu

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Securing Software

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Phishing

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<!DOCTYPE html>

<html>

…

<body>

…

</body>

</html>

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<a>Harvard</a>

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<a href="…">Harvard</a>

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<a href="https://harvard.edu">Harvard</a>

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<a href="https://harvard.edu">Harvard</a>

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<a href="https://harvard.edu">harvard.edu</a>

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<a href="https://harvard.edu">harvard.edu</a>

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<a href="https://harvard.edu">https://harvard.edu</a>

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<a href="https://harvard.edu">https://harvard.edu</a>

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<a href="https://yale.edu">https://harvard.edu</a>

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Code Injection

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Cross-Site Scripting

(XSS)

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<p>About 6,420,000,000 cats</p>

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<p>About 6,420,000,000 cats</p>

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<p>About 6,420,000,000 <script>alert('attack')</script></p>

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<p>About 6,420,000,000 <script>alert('attack')</script></p>

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Reflected

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Stored

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Character Escapes

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<p>About 6,420,000,000 <script>alert('attack')</script></p>

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<p>About 6,420,000,000 <script>alert('attack')</script></p>

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<p>About 6,420,000,000 <script>alert('attack')</script></p>

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< (<)

> (>)

& (&)

" (")

' (')

…

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Content-Security-Policy: script-src https://example.com/

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Content-Security-Policy: style-src https://example.com/

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SQL Injection

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SELECT * FROM users

WHERE username = '{username}'

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SELECT * FROM users

WHERE username = '{username}'

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malan

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malan'; DELETE FROM users; –-

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SELECT * FROM users

WHERE username = '{username}'

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SELECT * FROM users

WHERE username = 'malan'; DELETE FROM users; --'

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SELECT * FROM users

WHERE username = 'malan';

DELETE FROM users;

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SELECT * FROM users

WHERE username = '{username}' AND password = '{password}'

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SELECT * FROM users

WHERE username = '{username}' AND password = '{password}'

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malan

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' OR '1'='1

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SELECT * FROM users

WHERE username = 'malan' AND password = '' OR '1'='1'

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SELECT * FROM users

WHERE username = 'malan' AND password = ''

OR '1'='1'

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SELECT * FROM users

WHERE (username = 'malan' AND password = '')

OR '1'='1'

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SELECT * FROM users

WHERE '1'='1'

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Prepared Statements

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'

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''

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SELECT * FROM users

WHERE username = '{username}'

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SELECT * FROM users

WHERE username = ?

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SELECT * FROM users

WHERE username = 'malan''; DELETE FROM users; --'

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SELECT * FROM users

WHERE username = '{username}' AND password = '{password}'

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SELECT * FROM users

WHERE username = ? AND password = ?

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SELECT * FROM users

WHERE username = 'malan' AND password = ''' OR ''1''=''1'

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Command Injection

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system

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eval

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Developer Tools

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Client-Side Validation

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Server-Side Validation

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Cross-Site Request Forgery

(CSRF)

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GET

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POST

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</form>

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</form>

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</form>

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</form>

document.forms[0].submit();

</script>

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</form>

document.forms[0].submit();

</script>

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</form>

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</form>

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</form>

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POST / HTTP/3

Host: amazon.com

X-CSRFToken: 1234abcd

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Open Worldwide Application Security Project (OWASP)

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break

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Arbitrary Code Execution

(ACE)

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Remote Code Execution

(RCE)

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Buffer Overflow

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machine code

↑

stack

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machine code

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machine code

return address

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machine code

"go to machine code"

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machine code

cats

"go to machine code"

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machine code

"go to machine code"

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machine code

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machine code

return address

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machine code

"go to machine code"

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machine code

attack code

"go to machine code"

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machine code

attack code

…

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machine code

attack code

"go to attack code"

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Stack Overflow

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machine code

↑

stack

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Cracking

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Reverse Engineering

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Malware Analysis

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Open-Source Software

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Closed-Source Software

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App Stores

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software →

→ hash

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hash →

→ signature

private key →

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Package Managers

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Operating Systems

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Bug Bounty

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Common Vulnerabilities �and Exposures (CVE)

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National Vulnerability Database (NVD)

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Common Vulnerability Scoring System (CVSS)

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Exploit Prediction �Scoring System (EPSS)

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Known Exploited

Vulnerabilities Catalog (KEV)

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Introduction to

Cybersecurity

David J. Malan

malan@harvard.edu