As an application or network owner, we should know who or what is accessing our network resources. If we do not know or do not keep track of our activity and instead just assume what is happening on the network, we cannot guarantee data security and the safety of end-users.

We need to start with the basics of security. This begins with understanding what's on our network.

The most basic (but often most overlooked) element of network security involves keeping hardware protected from theft or physical intrusion.

As mentioned earlier, the first thing we need to classify is our assets. Once data classification is identified, network servers, network switches...

For managing network and networking assets, there must always be a centralized secure management utility subnet for services such as DNS, DHCP, NTP, AAA, and network management. By defining boundaries, it becomes much easier to troubleshoot problems with the services when they are in known locations with a few well-known access paths and methods.

Most of us focus on front door security and threats coming from the outside world by putting some sort of firewall on the perimeter. In reality, relying upon perimeter security alone does not protect your network and information data. Doing this is like putting money into a bank which depends on one armed guard.

The concept...

For any given operating system, tuning of the TCP/IP stack can be performed by the system administrator. Changing the default values of TCP/IP stack variables provides another layer of protection and helps you to secure your hosts in a better way.

This is all about determining and making decisions about how many connections the server can maintain in a half-open state before TCP/IP triggers SYN flooding attack protection. This simply means that to configure the threshold value of the TCP connection, requests must be exceeded before SYN flood protection is triggered.

The following parameters can be adjusted on an operating system level to tune TCP/IP stacks. These are not only applicable to the operating system, but also to network devices such as firewalls and load balancers, which allow you to fine tune TCP stacks:

• TcpMaxHalfOpen
• TcpMaxHalfOpenRetried...

A Denial-of-Service is an attack in which online services do not respond to connections from legitimate hosts due to their resources being overused by malicious requests. This attack becomes a Distributed Denial-of-Service (DDoS) attack when it comes from multiple sources and it becomes difficult to block the source with IP or Geo-location.

DDoS attacks usually take the form of the following:

• Volume-based attacks
• Application layer attacks
• Low-rate attacks

Volume based attacks are by far the most common type of DDoS attacks.

Volume-based attacks are characterized by an excessive amount of traffic...

IP spoofing is the creation of IP packets using somebody else's IP address as the source address of an IP packet.

Let's take a look at IP headers in an IP packet:

In the following diagram, the attackers represent someone else's IP address:

A network operator can implement an anti-spoofing access-list filter to prevent packets with incorrect source IP addresses from entering and leaving the network. With the following command, the access list will prevent incoming packets that have the internal IP address from coming in. 220.x.x.x is a network which I own, so I do not expect to encounter any packets coming from outside my own IP address.

Cisco IOS command:

access...

Let's try to understand ping before we discuss ping sweep.

• Ping: Ping is a tool commonly used to find the status of a host on a network. Ping is based on the ICMP protocol. When a Ping process request is sent out as an ICMP echo to the target host, it replies with an ICMP echo reply.
• Ping Sweep: Ping sweep is a technique that can be used to find out which hosts are alive in a network for a defined IP range. Network admins who allow ICMP are vulnerable to ICMP based attacks.

Multiple tools are available for ping sweeps. You can even develop your own tool with a small script. Here is a simple example of how to run a ping sweep from a Windows machine: FOR /L loop, which is a counter, the variable is %i. It starts at 1 and increases by 1 with each iteration through the loop, going up to 255. I want to ping through a ...

DNS continues to be a very attractive target for hackers and a very important piece of network from a user's point of view. We use it seamlessly almost every time we hit a web page or application throughout a day, without even knowing that it exists.

DNS provides a way to resolve the IP address of any host on the internet with directory services.

A host sends a DNS query request to a DNS server and, in response, gets the IP address 1.1.1.1 for  www.abc.com. The host can now make a direct request to www.abc.com using  the IP address: