re: Taskbar Issues
Friday, January 7, 2005 at 11:36 am
Windows XP Annoyances Discussion Forum
Posted by Falcon
(13489 messages posted)
First, you must understand how a computer program works internally. Imagine
that you're writing
a program that needs to do an operation several times in several places, such
as, for example, finding
the maximum value of a number.
if(X1 > X2)
X = X2
else
X = X1
if(Y1 > Y2)
Y = Y2
else
Y = Y1
if(Z1 > Z2)
Z = Z2
else
Z = Z1
As you see, this can get tedious to write and even more tedious to maintain.
Thus, functions were
introduced:
function min(First, Second) returns a Number
{
if(First > Second)
return First
else
return Second
}
X = min(X1, X2)
Y = min(Y1, Y2)
Z = min(Z1, Z2)
Now, as you see, the min is used in three places. How does the
computer know what it
should do next? Meet the stack:
The computer keeps track of what it must do next by placing the address of the
next instruction
after the function call onto the stack. You might think of the stack just like
a stack of papers,
for example. You can look at the top paper, remove the top paper, or put another
paper on top. In
a computer, the new item is added to the bottom (lowest address) of the stack,
however.
Perhaps you already see the problem--if computers usually copy data from the
lowest address to
the highest, but the stack grows from highest to lowest, what happens if a program
tries to copy
more data to the stack than space it reserved for that data? This is called a
buffer overrun (or overflow).
Thus, when the function returns, the injected code is run. Usually this code
is quite small,
and simply serves to load the remainder of the virus from somewhere else. For
Blaster, it uses the
TFTP protocol to transfer a file. For Slammer, the virus is contained completely
in the initial
attack.
The Wereotter
- Written in response to:
- re: Taskbar Issues (Alena: Friday, January 7, 2005 at 11:18 am)
There are presently no replies to this message.
|
|
All messages in this thread [show all]
 | | | |  |  | re: Taskbar Issues (Falcon: Fri, Jan 7, 2005, 11:36 am) |
| |
| |
Return to the Windows XP Discussion Forum
|
|
