8/27/26

Internet and the Web

DARPA laid down the ARPANet was laid to have quick communications during the Cold War. CERN then created the WWW. Internet is the hardware Web is the software.

8/31/26

3 way tcp

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Client Server architecture

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TCP

HTTP Request/Response

Client - Server System Client (Web Browser) sends the request Server sends the response

Sockets

When Connecting to website a socket is created Socket Connects network to OS Sockets are like radio channels, they are always all around us we have to tune into it.

Web Resources

Web resource is the source of web content

Static file on the web servers file system these files can contain anything:

• Text
• HTML
• Word
• Acrobat

Dynamic content resources generate content

• Based on identity
• Time of day

URI

Uniform Resource Identifier URLs and URNs are URI Http://www.joes-hardware.com/specials/saw-blade.gif Protocol, sub-domain, domain, sub directory, resource http - Use Http protocol www.joes-hardware.com - Go to www.hoes-hardware.com Grand the resource called specials/saw-blade.gif

URLs tell exactly where a resource is located and how to access it

Relative Paths

• Index.html
• /graphics/images.png
• /help/articles/how-do-i-setup-a-webpage.html

Absolute Paths

• https://www.mysite.com
• https://www.mysite.com/graphics/image.com
• https://www.mysite/help/articles/how-do-i-setup-a-webpage.html

9/7/26

TCP is so fun it has a six flags:

• SYN (Synchronize)
• ACK (Acknowledgment)
• FIN (Finish)
• RST (Reset)
• PSH (Push)
• URG (Urgent)

9/14/26

CA - entity that stores, signs, and issues digital certificates.

10/8/26

CIA Confidentiality Integrity Accessibility

File System Protections Set appropriate permissions on web content scripts and configuration files prevent file inclusion vulnerabilities

Data store protections prevent unauthorized access methods to databases and other backend data stores (eg prevent SQL injection)

Server Side script protections prevent script execution when not needed

Updates! OS as well as web server and backend applications

security specific technologies Security modules for web server (mod_security for apache) Os protection tools (eg SELinux) Intrusion Prevention systems denial of service protections web application firewall