Computer threat - Network Security

Every TCP package have 'flag bit’ defining content and intention of each package.

Example:

A package with flag bit contain "SYN or SYNCHRONIZE" will undertake to conduct initiation connection from sender to recipient. A package with flag bit contain "ACK" will undertake to inform receiver about sender information.
While a TCP package with beet flag contain "FIN" or "FINISH" undertaking to stop connection from sender to recipient.

To build a TCP connection, need data transfer package between two host, transfer of this data recognized by the name of "TCP Three-Way Handshake" as below picture.

Computer Network Threat

Threat is very harmful to the entire system and also by application at internal and external network.

The threat as follows:

Remote Login - this matter happened when someone capable to connect to a computer and have ability to control to several things related to resource found on the host or computer.

Application Backdoors - some program have special ability to access with long distance (remote access). Some bug program, exactly contain a backdoor or hidden access providing level control the computer and program.

SMTP session hijacking - SMTP is most commonly method used to deliver E-mail. By getting E-mail mailing-list, someone can deliver undesirable E-mail to thousands of or more users. This matter is called unsolicited junk mail or spam.

Spamming conducted with joining SMTP server which not suspect, then deliver thousands of E-mail called redirecting process, so that complicate to detect who is the real sender of the Mail Spam.

Operating system bugs – In application, some operation system have conducive security gap to be exploited illegally.

E-mail bombs - is an Individual attack, someone send hundreds or thousands of E-mail to one address so the victim E-mail cannot accept E-mail anymore.

Macro - To make simple or facilitate procedure an application, many application program permit us to make command which can be run by the program (script). By exploiting ability of script or macro, attacker can cause damage of data at computer.

Virus – Most known to make trouble at computer. The growth of virus from method, way of, making, effectiveness, damage storey, and also speed of spreading is different each other.

Redirect bombs – Hacker or Cracker can use ICMP to change direction of information and attack to other router.

Source routing - At many case, a data package which work through one or some network determined by router pass to route information by the router, but sometime hacker used the package as the real sender.

Another type of computer attack are from (next posted about this) :

Denial of Service (DoS)
Spoofing
Broadcast Amplification
TCP SYN

The method to run the threat above, can be conducted variously including using virus.

Network security - protecting PC

Tapping by hacker is an annoying problem when we are on surfing internet.

We have to learn how to hack but shall be used for protection from attack.

Following is tips and some software assisting to protect PC from online tapping.

Often we forget to protect our PC “attacking” from online tapping when we surf the internet.

Many civil people feel enough in protecting its PC with a program a kind of firewall desktop and anti spy firewall.

In fact, still many gap at firewall which you used, can be exploited by online watcher hacking on your PC

Below is a tips to protect PC from internet tapping in a LAN party, W-LAN or home connection as my experience.

Activated your Firewall:

In course of online tapping or infection, usually the first step do by hacker is collect information and data concerning victim to be tapped. Usually hacker use information compiler tools like “ Nmap” ( http://www.insecure.org/nmap), hereinafter hacker will check open port at victim PC and also TCP/IP package sent from PC into Network. This matter to get specific information is called print finger from victim PC.

The others way, hacker usually try to get deeper information by delivering an E-mail bait to victim (victim will open the e-mail through Microsoft Outlook program which integrated in its Windows). From bait E-mail answered, hence hacker directly can check what kind of E-mail software and server client install in victim PC.

A lot of “software bug” site, discuss about weak of E-mail software and server client according to each version, but I’m not talking about that weak at this post.

So how to avoid that attack ?

The way of which you can use as protection early is firewall desktop. If you do not wish to use special firewall or commercial, hence you enough activate personal firewall that found on Windows XP service pack 2. Comprehend firewall application path and activity which you use in order not to harm you.

Ascertaining your pc clear of Virus and Trojan, before install the firewall.
Configure your firewall with carefully in each application requiring to access online and also access sharing file in existing network.

Encrypt the Important Folder and WebMail connection.

After getting information about victim PC, usually hacker can start tapping, it is of course with two important tools that is " Ethereal" and "ARP-Spoofer". With ARP-Spoofer, hacker can take information which pass by victim PC with Gateway Internet access and that information package can be opened with “Ethereal (http://www.ethereal.com)”.

To overcome matter above, we have to encrypt our Webmail connection through https band. Do not use http band, better avoid to use ftp band and telnet, because can be sabotaged by hacker. You can use SSH connection to replace ftp band or the telnet. The existing constraint is there is very rare web server providing https service and the SSH.

One of the common Mail which use HTTPS is GMail. Whereas for the important and confidential folder in the PC better do Encrypt. Its data content with right click on folder that you want to Encrypt, its way open part: Properties – Advanced – Encrypt content to protect data. But this matter can be done if your XP windows system file is use NTFS type. By use NTFS system file, we also can block out to access rights access certain consumer.

Use Good Firewall.

With DNS spoofing, hacker can do deflection instructing PC victim to spurious website. This deflection is easy to do because DNS protocol is not have any security mechanism. This matter can be prevented by using good firewall application.

At firewall nowadays, usually DNS cache keep with elegantly, so when we ever visit to previous website, hence DNS spoofing we can prevent.

Recognize to access autoexec at registry

If hacker have succeeded tap your pc, usually they always prepare backdoor to facilitate hacking access in other opportunity. One of the effort draw up backdoor is by altering victim pc system file. But this matter can be easy to detect to through antivirus program.

The way of more realistic to all hacker by placing Trojan in our PC, then run through one of the "Autoexec" what running with autoexec in other Windows system. In anticipating this matter, which we do with install additional tools “Autorun” from Sysinternalsi (http://www.systernals.com).

With this tool can display lot of autoexec exist in our system. Autoruns also can show signature from autoexec exist in our pc system. If found autoexec entry which unknown and identify as trigger Trojan, hence Autoruns can turn off it. With this tool, we assisted in eliminating against backdoor which is possible left by hacker in our pc.

Besides trick above, to avoid tapping, suggested do not use User Administrator when surf in internet, then arrange your explorer internet security setting to High Level Security setting.

And don't forget to always Update your Windows, especially when newest update improve many Security system on your PC.