ATul Singh

A " Denial of Service" (DoS) attack is one where the attacker tries to make some resource too busy to answer legitimate requests, or to deny legitimate users access to your machine. Denial of service attacks have increased greatly in recent years. Some of the more popular and recent ones are listed below. Note that new ones show up all the time, so this is just a few examples. Read the Linux security lists and the bugtraq list and archives for more current information. SYN Flooding  - SYN flooding is a network denial of service attack. It takes advantage of a "loophole" in the way TCP connections are created. The newer Linux kernels (2.0.30 and up) have several configurable options to prevent SYN flood attacks from denying people access to your machine or services. Pentium "F00F" Bug  - It was recently discovered that a series of assembly codes sent to a genuine Intel Pentium processor would reboot the machine. This affects every machine with a Pe...

The BIOS is the lowest level of software that configures or manipulates your x86-based hardware. LILO and other Linux boot methods access the BIOS to determine how to boot up your Linux machine. Other hardware that Linux runs on has similar software (Open Firmware on Macs and new Suns, Sun boot PROM, etc...). You can use your BIOS to prevent attackers from rebooting your machine and manipulating your Linux system. Many PC BIOSs let you set a boot password. This doesn't provide all that much security (the BIOS can be reset, or removed if someone can get into the case), but might be a good deterrent (i.e. it will take time and leave traces of tampering). Similarly, on S/Linux (Linux for SPARC(tm) processor machines), your EEPROM can be set to require a boot-up password. This might slow attackers down. Another risk of trusting BIOS passwords to secure your system is the default password problem. Most BIOS makers don't expect people to open up their computer and disconnect batt...

Penetration testing, often called “pentesting”,“pen testing”, or “security testing”, is the practice of attacking your own or your clients’ IT systems in the same way a hacker would to identify security holes. Of course, you do this without actually harming the network. The person carrying out a penetration test is called a penetration tester or pentester. The difference between Penetration Testing and Hacking is that you have the system owner's permission to do testing and to identfiy security holes. If you want to do penetration testing u should better ask for his/her permission. Basic Security Concepts Vulnerability: It is a security hole in a piece of software, hardware of Operating system that provides a way to attack the system.A vulnerabilty is as simple as weak passwords and as complex as buffer overflows as well as SQL injection. Security Research: Vulnerabilities are typically searched by security researchers who finds the flaws in the system. Security Research can ...

DHCP is a protocol that permits dynamic assignment of IP numbers. This replaces the labor-intensive process of IP address management, in which every host is configured with a static IP number assigned to it. DHCP allows the centralization and automation of the IP assignment process. Hosts are leased an IP number for a given amount of time, and this makes the process of managing and administering large networks more efficient. This is good for the network administrator, but makes the security administrator's job more complicated (for example, when some IP number and associated temporary owner have to be chased down for questionable activity). Computers that are connected to non-DHCP equipped IP networks must be configured before they can communicate with other computers on the network. DHCP allows a computer to be configured automatically, eliminating the need for intervention by a network administrator. It also provides a central database for keeping...