Category: Linux

This question has not yet appeared in my inbox, although since I have already written an explanation on the meaning of the term “Sniffer” it makes sense to write one about a tool commonly used in conjunction with a “Sniffer”. So here is an explanation on what a “Scanner” is and what it may be used for. Note I am referring to a “Network Scanner” not an optical scanner.

A “Scanner” is a shortened term for “Network Scanner”. The “Network Scanner” is a software program that can be used to passively scan for network broadcasting devices, such as a wireless access point (AP) that could potentially be exploited in order to gain unauthorized access into a system belonging to the network connected to this wireless access point, or perhaps authorized access assuming you have permission from the owner of the network or computer to perform a security audit.


By using the term “Passive Scan” I am referring to a scan in what is commonly known to security enthusiasts as a scan in “Monitor Mode”. This means that the wireless device will only capture data packets and broadcast beacons without sending and data packets. Thus making you much less likely to be discovered by the owner of the device or devices that you are collecting data packets from. I would also like to note that in most circumstances collecting wireless packets should be no more illegal than say peering into your neighbour’s lounge room through the front door that he left open. It is in principle no different. Just be sure that if you do choose to pursue the data packets of your surrounding access points that the owner of them is not a security freak or a person with a great lawyer, as this could result in them turning the tables on you and getting you in trouble.


Due to the haze between the terms “Sniffer” and “Scanner” personal opinions on each may vary. My preference in network sniffers would be Wireshark and my preference in “Scanner” would be Airodump-ng.

I hope that this has helped you understand the meaning of the term “Scanner” when referring to network security. Have fun testing your network from the outside, perhaps it is not as secure as you may have once thought.


This question has been rolling into my inbox quite frequently over the past weeks and I have written the answer to the question below.

Please note that this is not a complete guide to the entirety of 802.11 as such, it is more of a basic outline that any intermediate to advanced computer user should be able to understand.


Most people with a lack of knowledge related to computing will hear the term “802.11” and immediately think “Wi-Fi”. 802.11 is not necessarily “Wi-Fi” but it is more a term for the standard of such. In short 802.11 is actually more seldom referred to as the 802.11 standard. Meaning that a wireless device should comply with the 802.11 standard in order to be compatible with the majority of wireless devices located around the world. In addition you may like to know that the 802.11 standard in itself defines a link layer wireless protocol, which is managed by a committee known as “IEEE” (a.k.a The Institute of Electrical and Electronics Engineers). As an additional note “Wi-Fi” and “802.11” are similar in principal but are not the same thing.


The history of the 802.11 standard is a long one, which I will condense for you.


The first 802.11 standard was formally approved in the year 1997. This standard would transmit a maximum of 2Mbps (Mega bits per second).


The next standard that was approved and released was in the year of 1999, it was the “802.11b” standard, which was what you could call an add-on to the original “802.11” standard. The “802.11b” standard allowed what seemed then to be a mind-blowing data transfer rate of 11Mbps (11 Mega bits per second).


After “802.11b” the “802.11a” protocol was approved and released in 1999, which was oddly enough the same year as the release of its predecessor “802.11b”. This new protocol allowed transmission across the 5Ghz radio band, which in turn reduced interference and crowding across the cliché 2.4Ghz band that still to this day seems to run everything with an antenna. This new protocol allowed a much higher speed due to different transmission techniques and a less congested band, which was a whopping 54Mbps (54 Mega bits per second).


Later on in 2003 the IEEE approved and released another new 802.11 protocol standard, which was named 802.11g, which provided the same data transfer rate of 54Mbps (54 Mega bits per second) as the “802.11a”, although it returned to the 2.4Ghz band that was used in most protocol standards prior to the “802.11a” standard. This return to the 2.4Ghz band while offering the same data transfer rate attracted corporations and the general public to adopt the idea and even today it remains one of the most commonly used 802.11 protocols in use.


Shortly after the release of the “802.11g” protocol standard, a new protocol was approved and released. This was the “802.11n” protocol standard, which allowed a colossal 100Mbps (100 Mega bits per second) data transfer rate. Although it is still not as widely known and used as the “802.11g” protocol standard.

That is the basic outline of 802.11. I hope that this has answered your question sufficiently.

This question is one that I do get very rarely, although I know that there are a few of you security savvy computer users like myself out there who would love to know exactly what the term “Sniffer” refers to.

A “sniffer” is a software program, which can be either command-line or GUI based. This software program is used to monitor every single data packet that travels through a specific network interface on the computer of which it is running on.


For example you decide to run Wireshark (formerly Ethereal) on your computer whilst being connected to your home network. Wireshark is a network sniffer. While you run this software you must then select the network device of which you would like to observe packet data on. Say you were connected to your home network wirelessly using a Broadcom wireless device, which was named “Wlan0” on your computer, you would run Wireshark and select the capture device “Wlan0” and then click the “Start Capture” button at the top of the software window, which would begin capturing all of the data packets sent across your wireless device.


Knowing what data packets are flowing across your wireless device that is connected to your home network without internet access is rather pointless, although say you were connected to the internet or you were running a web server on the computer you are running Wireshark on, you would be much more likely to detect an attack and shut down your server to prevent any damage from the attack.

I am sure that this has enlightened you as to the meaning of the term “Sniffer”. You are now one step closer to knowing how to secure your network.

What are “runlevels” in Ubuntu?

Quite simply a “runlevel” is a state in Ubuntu, which is neither “On” or “Off” but a state in between the two.

A “runlevel” exists in Ubuntu because, unlike other operating systems, Ubuntu allows for different states of operation. These “runlevels” influence which processes are loaded at bootup on a Ubuntu system. These processes being controlled are usually very important processes, such as mounting HDDs on boot or sending output to the input of your monitor.


By default all boot processes will be run automatically at boot, although by editing the file that controls the “runlevels” you are able to decide exactly which processes start and in which order.


There are several “runlevels” in Ubuntu. They are listed below:

Runlevel Number Runlevel Function
Runlevel 0 This runlevel is also known as “halt” in that it is used to shutdown Ubuntu.
Runlevel 1 This runlevel is unique in that it boots to a shell prompt which will allow a login, although this login must be to the root account only as no other account logins are accepted. This is used for root changes to the system when a graphical interface must not be used, such as installing graphics drivers or updating some system files.
Runlevel 2 This is the regular runlevel for Ubuntu and is used by default.
Runlevel 3 This particular runlevel is not used in Ubuntu, although it is used in an array of other Linux distributions.
Runlevel 4 This particular runlevel is not used in Ubuntu, although it is used in an array of other Linux distributions.
Runlevel 5 This particular runlevel is not used in Ubuntu, although it is used in an array of other Linux distributions.
Runlevel 6 This runlevel is used to restart the Ubuntu system.

I hope that this piece has informed you on the uses of runlevels on Ubuntu, Kubuntu and Xubuntu. Enjoy your newfound Linux knowledge.

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