Firewall Technologies: Packet Filtering, Proxy, and Stateful Inspection
Firewall Technologies
Packet filtering – Packets (small chunks of data) are analyzed against a set of filters. Packets that pass the filters are sent to the requesting system; all others are discarded.
Proxy service – Information from the Internet is retrieved by the firewall and then sent to the requesting system and vice versa.
Stateful inspection – A newer method that doesn’t examine the contents of each packet but instead compares certain key parts of the packet to a database of trusted information.
Read MoreJava Code Snippets: Database, Lambda, and String Operations
Database URL: jdbc:mysql://mis-sql.uhcl.edu/agarwaln8497
agarwaln84971005681String errorMsg = "";Connection c = null;Statement s = null;ResultSet rset = null;Submit Method
This method handles database connection and data retrieval.
public String Submit() {
try {
Class.forName("com.mysql.jdbc.Driver");
System.out.println("Driver is ok.");
} catch (ClassNotFoundException Database Recovery Techniques and Security
Purpose of Database Recovery
To bring the database into the last consistent state, which existed prior to the failure.
To preserve transaction properties (Atomicity, Consistency, Isolation, and Durability).
Types of Failure
Transaction failure: Transactions may fail because of incorrect input, deadlock, or incorrect synchronization.
System failure: System may fail because of addressing error, application error, operating system fault, RAM failure, etc.
Media failure: Disk head crash, power disruption,
Read MoreUnderstanding Computer Networks: Protocols, Types, and Security
Computer Networks
Internet Protocols & Hardware
Internet communication relies on a set of rules and protocols, similar to how humans communicate. Internet hardware enables the connection.
- Examples: TCP, Ethernet, Handshaking, UDP, FTP, HTTP, Telnet, SSH. Network hubs, switches, routers, and dedicated cabling are examples of network hardware.
- Applications: Internet protocols are applied to network hardware to enhance security.
Network Types
LANs – Local Area Network
A LAN serves a local area, typically
Java Servlet and Swing Code Examples
Result Servlet
This servlet generates random numbers and forwards to Guess.html.
import java.io.IOException;
import java.io.PrintWriter;
import java.util.Random;
import javax.servlet.RequestDispatcher;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
@WebServlet(
Billing System: Data, Processes, and Meter Management
Billing System Reference Data
Overview of Billing System
Description of flow of information amongst various modules belonging to the Billing System.
Description of Customer Account modelling + table design.
Category, Supply Type association determining Tariff
Association between accounts – Bulk Meter, Docker’s Flat
Description of Living Quarters
Grouping of Accounts by walks, sections, areas for meter reading.
Flags: Bill NOT Bill, Disconnection Flag
Description of views: bil_vat_categories, bil_item,
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