November 18, 2011

Assignment 3 - Theoretical Part

More details about chmod.

What is chmod?

chmod is a Unix command that lets you tell the system how much (or little) access it should permit to a file.First let's see something about permissions.

As you see this columns at green highlighter is the permission that have every file.

If you see in the next picture the first set three letters after the file type tell what you, the owner of the file, have permission to do.An r in the first position means you are permitted to read the file. A w in the second position means you may write the file. This includes the ability to delete a file. An x in the third position means you may execute the file.

A hyphen in any position means that you don’t have that particular permission.
The last three letters in the permissions column tell us what everyone else in the world, the “others” may do.

The “others” lead highly restricted lives. They can’t write any files or directories, and they have absolutely no access to the topsecret.inf file.

We use the chmod command to change the access mode of a file. This command comes in many flavors, but we'll be talking primarily about one of them.
chmod who=permissions filename
This gives “who” the specified permissions for a given filename.

In this example publicity.html for reading and writing by anyone.

In this example we make all permissions for the group for topsecret.inf.

In this example we make a permission for one user


What is phishing?

Phishing refers to online scams that attempt to trick consumers into revealing personal information, such as check and credit card account numbers, Social Security numbers, or bank account passwords. Most commonly, phishers target unsuspecting users with fake Internet sites or email messages that look startlingly similar to the real thing. This is sometimes referred to as “spoofing.” Scammers may also leverage social networking sites, where users are already accustomed to sharing information with others.

How does phishing work?

Phishing emails and websites typically use familiar logos and graphics to deceive consumers into thinking the sender or website owner is a government agency, bank, retailer or other company they know or do business with. Sophisticated phishers may include misleading details, such as using the company CEO’s name in the email “from” field. Another common phishing tactic is to make a link in an email (and the fake website where it leads) appear legitimate by subtly misspelling URLs or changing the “.com” to “.biz” or another easily overlooked substitution.


  1. Other common protocol(slide 8) is telnet, i have used that protocol to administrate remotely routers, you just need to know the ip address of the equipment that you want to administrate(routers telmex normally have address). To use this protocol you can do "telnet" in terminal or cmd.

  2. To complement your opinion, telnet, has the advantage that is fast, doesn't ask permission, easy way to create users, but the sad truth is that it has a disadvantage about their safety which doesn't encrypt data in the delivery. The conclusion at which I arrive is that to do things remotely from a distance is recommended to use SSL as encrypted and is safe, and optionally,will be accepted telnet at local connection and you won't expose you a lot.

  3. Another disadvantage I see about telnet is that it doesn't encrypt any password, so it can be easily accessed and the packets may be intercepted.

  4. could be implemented in the presentation a little more than network, for example, client-server architecture, peer to peer, these models use the communication protocols you mentioned:)

  5. In addition to the 10+2 awarded on the day of the presentation, +1 is given for extra contents in the blog.