1. The document discusses SSH, Telnet, and proxy servers. SSH provides encrypted connections over unsecured networks, while Telnet lacks encryption. Proxies act on behalf of users to access resources, with forward proxies providing external access through a firewall and reverse proxies providing internal access from outside. 2. It provides examples of Linux commands to switch users using SSH, copy a file between accounts using sudo, and set file permissions using chmod and chown.

1. NATIONAL INSTITUTE OF TRANSPORT
DEPARTMENT OF COMPUTING AND COMMUNICATION TECHNOLOGY
(CCT)
Individual Assignment 1
On the course Information System Security (ITU 08104)
Done by:
NIT/BSCIT/2013/06
Konzo, Eliya W.
Submitted to:
Mr. Lott, Champs.

2. 1. Explaining SSH, Telnet and Proxy
SSH
Secure Shell, or SSH, is a cryptographic (encrypted) network protocol operating at layer 7 of the OSI
Model to allow remote login and other network services to operate securely over an unsecured
network.
SSH provides a secure channel over an unsecured network in a client-server architecture, connecting
an SSH client application with an SSH server. Common applications include remote command-line
login and remote command execution, but any network service can be secured with SSH
Telnet
Telnet is a client-server protocol, based on a reliable connection-oriented transport. Typically, this
protocol is used to establish a connection to Transmission Control Protocol (TCP) port number 23,
where a Telnet server application (telnetd) is listening. Telnet, however, predates TCP/IP and was
originally run over Network Control Program (NCP) protocols.
Proxy
“Proxy” is a general term that means “to act on behalf of a user in an authorized capacity.” A web
proxy server intercepts client connections and obtains the requested content from an origin server,
the owner of the content on behalf of the client.
A typical web proxy accepts connections from clients, makes decisions as to whether the clients are
permitted to use the proxy or access the requested resources, and then completes connections on
behalf of the clients to the various origin servers. In this manner, the web proxy acts as both a server
as well as a client of the requested resource.
The two basic types of web proxy server are: a forward proxy and a reverse proxy
i. Forward Proxy Scenario
A Forward proxy provides internal clients access through a firewall to resources on the
Internet. This service is often provided as part of a larger intranet security strategy. Forward
proxying allows clients to access resources outside of the firewall without compromising the
integrity of the private network.
A forward proxy can be configured to keep copies of content within their local cache.
Subsequent requests for that content can then be serviced from the local cache rather than
obtaining the content from the origin server. Caching increases performance by decreasing the
time involved in traversing the network.
Most proxy servers have the capability to filter requests from users. Administrators can
choose to limit access to certain resources that might not be appropriate for the workplace and
therefore deny such access.

3. In a forward proxy scenario, the client is aware of the proxy server and is configured to use
it for various requests. The firewall can then be configured to allow only certain traffic from the
proxy server rather than permitting such access to all internal clients.
ii. Reverse Proxy Scenario
A proxy server can also provide external clients with access to internal resources the reside
behind the corporate firewall. When a proxy server is used to handle connections into a private
network, the process is called reverse proxying. The term “reverse” refers to the fact that traffic
flows in the opposite direction from normal proxy traffic flow.
A forward proxy is best used to filter content, increase performance, and log user accesses.
A reverse proxy provides these benefits and more. You can use a reverse proxy to load balance
across multiple servers, provide failover capabilities, and provide access to corporate resources
in a safe and secure manner.
In a reverse proxy scenario, the client is not even aware that it is using a proxy server. This
transparency is one of the key differences between a forward and reverse proxy server scenario.
2. Provide a valid command which ca be used to switch from account A to account B using SSH.
To switch user on SSH the following command is used
[A@server]$ ssh B@server
The window will then prompt for password of user B
3. A valid command which ca be used to copy file named Data from account A to account B
To copy a file named data from account A to account B the following command might be used
A@server:~$ sudo cp /home/A/data /home/B/
Sudo was used to gain access to B’s Account
4. Write a Linux command to set the following permission to a file
i. -rwxrwxr-x 1 juan student 0 Sep 26 12:25 test
ii. –rwxrw-r-x 1 juan student 0 Sep 26 12:25 test
To change permission, the following commands can be used
i. To change file permission to -rwxrwxr-x, we use.
:$ chmod 775 test
to change owner to juan and owner-group to student
:$ chown juan:student test

4. ii. To change file permission to -rwxrw-r-x, we use.
:$ chmod 765 test
to change owner to juan and owner-group to student
:$ chown juan:student test