Showing posts with label Basics. Show all posts
What is a Computer Virus ?
A potentially damaging computer programme capable of reproducing itself causing great harm to files or other programs without permission or knowledge of the user.
Types of viruses :-
The different types of viruses are as follows-
1) Boot Sector Virus :- Boot sector viruses infect either the master boot record of the hard disk or the floppy drive. The boot record program responsible for the booting of operating system is replaced by the virus. The virus either copies the master boot program to another part of the hard disk or overwrites it. They infect a computer when it boots up or when it accesses the infected floppy disk in the floppy drive. i.e. Once a system is infected with a boot-sector virus, any non-write-protected disk accessed by this system will become infected.
Examples of boot- sector viruses are Michelangelo and Stoned.
2) File or Program Viruses :- Some files/programs, when executed, load the virus in the memory and perform predefined functions to infect the system. They infect program files with extensions like .EXE, .COM, .BIN, .DRV and .SYS .
Some common file viruses are Sunday, Cascade.
3) Multipartite Viruses :- A multipartite virus is a computer virus that infects multiple different target platforms, and remains recursively infective in each target. It attempts to attack both the boot sector and the executable, or programs, files at the same time. When the virus attaches to the boot sector, it will in turn affect the system’s files, and when the virus attaches to the files, it will in turn infect the boot sector.
This type of virus can re-infect a system over and over again if all parts of the virus are not eradicated.
Ghostball was the first multipartite virus, discovered by Fridrik Skulason in October 1989.
Other examples are Invader, Flip, etc.
4) Stealth Viruses :- These viruses are stealthy in nature means it uses various methods for hiding themselves to avoid detection. They sometimes remove themselves from the memory temporarily to avoid detection by antivirus. They are somewhat difficult to detect. When an antivirus program tries to detect the virus, the stealth virus feeds the antivirus program a clean image of the file or boot sector.
5) Polymorphic Viruses :- Polymorphic viruses have the ability to mutate implying that they change the viral code known as the signature each time they spread or infect. Thus an antivirus program which is scanning for specific virus codes unable to detect it's presense.
6) Macro Viruses :- A macro virus is a computer virus that "infects" a Microsoft Word or similar application and causes a sequence of actions to be performed automatically when the application is started or something else triggers it. Macro viruses tend to be surprising but relatively harmless.A macro virus is often spread as an e-mail virus. Well-known examples are Concept Virus and Melissa Worm.
Tag :// Basics,
Tag :// Creat virus
Hello friends,How r you ?In this post,I am writing some hacks that are present in the Internet 24/7 and not noticed by Website Administrator.This hack is also based on Google Hacking and SQL Injection.So,First You need to know.....
WHAT IS SQL INJECTION:
SQL Injection is one of the most common vulnerability on the WEB.Well if you are not familiar with programming language and Scripting then you are wondering What SQL means.SQL is Structured Query Language.
At Present,Most of the Website has Database (eg MySQL) which is stored on there server and is accessible to website administrator only b/z He/She has Username and Password to access the Database.
Ok,Let's take a simple example:
You are surfing on NET and want to open GMAIL,FACEBOOK etc.First thing you have to do is to put your USERNAME and PASSWORD in the LOGIN BOX and after that you will see that your Page is opening.So,What is happening behind the screen or behind the server.When you click on Submit button then your USERNAME and PASSWORD will go to database of server which is stored at their server.And if it is correct then you are Authorized to Enter in next page else not.
When the server receives the username and password strings he will query the database to see if the supplied credentials are valid. He will use an SQL statement for that that may look like this:
SELECT * FROM users WHERE username='xxxxxxx' AND password='xxxxxxxxx'
For those of you who are not familiar with the SQL language, in SQL the ‘ character is used as a delimiter for string variables. Here we use it to delimit the username and password strings supplied by the user.
In this example we see that the username and password supplied are inserted into the query between the ‘ and the entire query is then executed by the database engine. If the query returns any rows, then the supplied credentials are valid (that user exists in the database and has the password that was supplied).
Now, what happens if a user types a ‘ character into the username or password field? Well, by putting only a ‘ into the username field and leaving the password field blank, the query would become:
SELECT * FROM users WHERE username=''' AND password=''
This would trigger an error, since the database engine would consider the end of the string at the second ‘ and then it would trigger a parsing error at the third ‘ character. Let’s now see what would happen if we would send this input data:
Username: ' OR 'a'='a Password: ' OR 'a'='a
The query would become
SELECT * FROM users WHERE username='' OR 'a'='a' AND password='' OR 'a'='a'
Since a is always equal to a, this query will return all the rows from the table users and the server will “think” we supplied him with valid credentials and let as in – the SQL injection was successful .
Now we are going to see some more advanced techniques.. My example will be based on a PHP and MySQL platform. In my MySQL database I created the following table:
CREATE TABLE users ( username VARCHAR(128), password VARCHAR(128), email VARCHAR(128))
There’s a single row in that table with data:
username: testuser password: testing email: testuser@testing.com
To check the credentials I made the following query in the PHP code:
$query="select username, password from users where username='".$user."' and password='".$pass."'";
The server is also configured to print out errors triggered by MySQL (this is useful for debugging, but should be avoided on a production server).
So, last time I showed you how SQL injection basically works. Now I’ll show you how can we make more complex queries and how to use the MySQL error messages to get more information about the database structure.
Lets get started! So, if we put just an ‘ character in the username field we get an error message like You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near ”” and password=”’ at line 1
That’s because the query became
select username, password from users where username=''' and password=''
What happens now if we try to put into the username field a string like ‘ or user=’abc ? The query becomes
select username, password from users where username='' or user='abc ' and password=''
And this give us the error message Unknown column ‘user’ in ‘where clause’
That’s fine! Using these error messages we can guess the columns in the table. We can try to put in the username field ‘ or email=’ and since we get no error message, we know that the email column exists in that table. If we know the email address of a user, we can now just try with ‘ or email=’xyz@xyz.com in both the username and password fields and our query becomes
select username, password from users where username='' or email='xyz@xyz.com' and password='' or email='xyz@xyz.com'
which is a valid query and if that email address exists in the table we will successfully login!
You can also use the error messages to guess the table name. Since in SQL you can use the table.column notation, you can try to put in the username field ‘ or user.test=’ and you will see an error message like Unknown table ‘user’ in where clause
Fine! Let’s try with ‘ or users.test=’ and we have Unknown column ‘users.test’ in ‘where clause’
so logically there’s a table named users .
Basically, if the server is configured to give out the error messages, you can use them to enumerate the database structure and then you may be able to use these informations in an attack.
WHAT IS SQL INJECTION:
SQL Injection is one of the most common vulnerability on the WEB.Well if you are not familiar with programming language and Scripting then you are wondering What SQL means.SQL is Structured Query Language.
At Present,Most of the Website has Database (eg MySQL) which is stored on there server and is accessible to website administrator only b/z He/She has Username and Password to access the Database.
Ok,Let's take a simple example:
You are surfing on NET and want to open GMAIL,FACEBOOK etc.First thing you have to do is to put your USERNAME and PASSWORD in the LOGIN BOX and after that you will see that your Page is opening.So,What is happening behind the screen or behind the server.When you click on Submit button then your USERNAME and PASSWORD will go to database of server which is stored at their server.And if it is correct then you are Authorized to Enter in next page else not.
When the server receives the username and password strings he will query the database to see if the supplied credentials are valid. He will use an SQL statement for that that may look like this:
SELECT * FROM users WHERE username='xxxxxxx' AND password='xxxxxxxxx'
For those of you who are not familiar with the SQL language, in SQL the ‘ character is used as a delimiter for string variables. Here we use it to delimit the username and password strings supplied by the user.
In this example we see that the username and password supplied are inserted into the query between the ‘ and the entire query is then executed by the database engine. If the query returns any rows, then the supplied credentials are valid (that user exists in the database and has the password that was supplied).
Now, what happens if a user types a ‘ character into the username or password field? Well, by putting only a ‘ into the username field and leaving the password field blank, the query would become:
SELECT * FROM users WHERE username=''' AND password=''
This would trigger an error, since the database engine would consider the end of the string at the second ‘ and then it would trigger a parsing error at the third ‘ character. Let’s now see what would happen if we would send this input data:
Username: ' OR 'a'='a Password: ' OR 'a'='a
The query would become
SELECT * FROM users WHERE username='' OR 'a'='a' AND password='' OR 'a'='a'
Since a is always equal to a, this query will return all the rows from the table users and the server will “think” we supplied him with valid credentials and let as in – the SQL injection was successful .
Now we are going to see some more advanced techniques.. My example will be based on a PHP and MySQL platform. In my MySQL database I created the following table:
CREATE TABLE users ( username VARCHAR(128), password VARCHAR(128), email VARCHAR(128))
There’s a single row in that table with data:
username: testuser password: testing email: testuser@testing.com
To check the credentials I made the following query in the PHP code:
$query="select username, password from users where username='".$user."' and password='".$pass."'";
The server is also configured to print out errors triggered by MySQL (this is useful for debugging, but should be avoided on a production server).
So, last time I showed you how SQL injection basically works. Now I’ll show you how can we make more complex queries and how to use the MySQL error messages to get more information about the database structure.
Lets get started! So, if we put just an ‘ character in the username field we get an error message like You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near ”” and password=”’ at line 1
That’s because the query became
select username, password from users where username=''' and password=''
What happens now if we try to put into the username field a string like ‘ or user=’abc ? The query becomes
select username, password from users where username='' or user='abc ' and password=''
And this give us the error message Unknown column ‘user’ in ‘where clause’
That’s fine! Using these error messages we can guess the columns in the table. We can try to put in the username field ‘ or email=’ and since we get no error message, we know that the email column exists in that table. If we know the email address of a user, we can now just try with ‘ or email=’xyz@xyz.com in both the username and password fields and our query becomes
select username, password from users where username='' or email='xyz@xyz.com' and password='' or email='xyz@xyz.com'
which is a valid query and if that email address exists in the table we will successfully login!
You can also use the error messages to guess the table name. Since in SQL you can use the table.column notation, you can try to put in the username field ‘ or user.test=’ and you will see an error message like Unknown table ‘user’ in where clause
Fine! Let’s try with ‘ or users.test=’ and we have Unknown column ‘users.test’ in ‘where clause’
so logically there’s a table named users .
Basically, if the server is configured to give out the error messages, you can use them to enumerate the database structure and then you may be able to use these informations in an attack.
Tag :// Basics
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