# --> "virus.exe" <--

You have just arrived at work and walked to your cubicle, and after checking your emails, you are about to get started with your project, when you notice a strange new application on your desktop. The text under the application icon is simply "virus.exe", and this was what the icon looked like:

Thinking this is one of the normal pranks that your coworkers play on you all the time, you laugh as you click on the application to open it. The smile quickly fades from your face as your screen suddenly goes blank. After a few seconds, your screen turns a bright white, and a few numbers appear on the screen:

7 5 4 3

The numbers disappear and the following appears on the screen:

Wtdepy ez xj hzcod ty estd wpeepc
Wtvp eszdp ez rz zy tyez esp wtrse
Te htww mp ty esp xfdtn
Ty esp vpj zq N dslca

You quickly get your phone and take a picture of the screen right before the computer monitor goes blank again. After another few seconds, your screen turns normal again. A dialog box shows up in the center of your screen, and the following is what you saw:

Hello again,
By now, you must have realized that this is indeed no joke. Dont worry, though; if you follow our directions, nobody will be hurt. What just happened to your computer is the same thing that is happening to a select few across the globe right now. You are one of the lucky ones. The task here is simple: below this message is a spot where you can enter four different characters. These characters can be letters or numbers (not case sensitive). All you have to do is put in the right four characters and we will be on our merry way.
Your computer will not be harmed. Don't call the police, don't tell your boss. Don't tell anybody, because if you do, there will be trouble for you ahead. You have an hour to figure out the code. We're watching

Below the message was indeed a spot for you to enter four characters. Next to that was a small button that said 'Enter'. Below that was a set of clues.

00100000 00100000 00100000 01011111 01011111 01011111
01011111 01011111 01011111 01011111 00001101 00001010
00100000 00100000 00101111 01011111 01011111 01011111
01011111 01011111 01011111 01011111 01011100 00001101
00001010 00100000 00100000 01111100 00100000 00100000
00100000 01011111 00100000 00100000 00100000 01111100
00001101 00001010 00100000 00100000 01111100 00100000
00100000 01111100 00100000 01111100 00100000 00100000
01111100 00100000 00111110 01001010 00101000 00110011
00101001 00111100 00100000 00100000 00100000 00100000

00100000 00100000 00100000 00100000 00100000 00101110
00101101 00101101 00101110 00001101 00001010 00101110
00101101 00101101 00101101 00101101 00100111 00100000
00100000 00100000 00100111 00101101 00101101 00101110
00001101 00001010 00100111 00101101 00101000 00101001
00101101 00101101 00101101 00101101 00101101 00101000
00101001 00101101 00100111 00100000 00111110 00110110
00101000 00110001 00101001 00111100 00100000 00100000

00100000 00101110 00101101 00101101 00101110 00001101
00001010 00101111 00101110 00101101 00101110 00100000
00100111 00101101 00101101 00101101 00101101 00101101
00101101 00101101 00101101 00101101 00101101 00101110
00001101 00001010 01011100 00100111 00101101 00100111
00100000 00101110 00101101 00101101 00100010 00101101
00101101 00100010 00100010 00101101 00100010 00101101
00100111 00100000 00111110 01000001 00101000 00110010
00101001 00111100 00001101 00001010 00100000 00100111
00101101 00101101 00100111 00100000 00100000 00100000

00100000 00100000 01101111 01001111 01001111 01001111
01001111 01001111 01101111 00001101 00001010 00100000
00101100 01111100 00100000 00100000 00100000 00100000
01101111 01001111 00001101 00001010 00101111 00101111
01111100 00100000 00100000 00100000 00100000 00100000
01111100 00001101 00001010 01011100 01011100 01111100
00100000 00100000 00100000 00100000 01111100 00001101
00001010 00100000 00100000 00100111 00101101 00101101
00101101 00101101 00101101 00100111 00100000 00111110
01011010 00101000 00110011 00101001 00111100 00100000
00100000 00100000 00100000 00100000 00100000 00100000

x = ?
2^(x-1)=2(4^(x/3)) >x(1)<

.

z = ?
1 = 5
2 = 10
3 = 20
4 = 15
5 = z >z(4)<

HINTS (These are in no particular order)
Hint 1:

Think of conversion with the binary

Hint 2:

The numbers in the beginning correspond to a message

Hint 3:

This one is very simple. Look at the equations. Read it.

Hint 4:

This one involves some math. Try to write the equation on a piece of paper and solve it. Knowing exponent rules is very helpful.

• Do you plan on adding hints? Oct 23 '18 at 16:56
• IIRC, if you put only one number indicator at the front, all the following letters that are possible numbers are automatically considered digits of that number. So the second number indicator probably shouldn't be there; now it kind of reads as "one, five". (Haven't tried to solve the problem though, maybe it's intentional.)
– Bass
Oct 23 '18 at 18:02
• The new binary gave me a different (possibly incorrect) solution for the fourth item than the previous version did.
– Jo.
Oct 24 '18 at 5:49
• Sorry, I'm a Linux user, Mr. Evil Genius! I like your puzzle, +1.
– hat
Oct 24 '18 at 6:39
• I am the only who was afraid to click on this puzzle's title ? Oct 25 '18 at 14:29

For the binary code:

I converted each to decimal, then printed the ascii character corresponding to the decimal number.

   _______
/_______\
|   _   |
|  | |  | >J(3)<

.--.
.----'   '--.
'-()-----()-' >6(1)<

.--.
/.-. '----------.
\'-' .--"--""-"-' >A(2)<
'--'

oOOOOOo
,|    oO
//|     |
\\|     |
'-----' >Z(3)<

The tic-tac-toe board:

SCRATCH. The game is a draw, also known as a Cat Scratch (although, when growing up, I only ever knew of it as a CAT), which is also what appears to be scratched across it. The (3) is near the bottom right x, so going with the other parts of the puzzle, >x(3)<, though I have no idea what this notation means.

• Hint: think of the first letter when the answer is a word. You are very close, it is not cat, but another word for a tie in tic tac toe Oct 25 '18 at 17:44

rot 15 (if I'm not mistaken) but rot 11 gives the following translation of the four lines:
Listen to my words in this letter
Like those to go on into the light
It will be in the music
In the key of C sharp

The equation's solution is:

x = 6, and because it has >x(1)<
in the solution digit (1) = 6

A guess the tic-tac-toe solution is:

0, because nobody won in this game,
so digit (3) = 0

The number sequence:

Not sure on this one but https://oeis.org/A300019 matches the sequence.
I didn't understand how the sequence work, but the next digit is 1
So I'm putting my bet on digit (4) = 1

As for the remaining bits I haven't yet used the digits 7 5 4 3 or the binary code. What puzzles me about it is that not all the lines are equaly long because not all of the numbers are 8 bit.

• The rot15 part likely means it was encoded in rot15 and that's why you can decode it with rot11 Oct 23 '18 at 12:10
• I fixed the binary issues. All of them are 8-bit now. Oct 24 '18 at 0:24

Assuming the dots on the bottom of the virus icon is braille that translates to :

rot#a#e

Which might be another hint to come in handy.

The binary converted to ascii values gives :

_______@@^��������(������|����Q�����QA�I�qiip������rr���D�%�����%����%'�ť�ˋK� �KKKKKKKKKK�.K

Trying different conversions in a bit.

The last hint puzzles me a bit, not sure what the > (bigger then) and < (smaller then) symbol mean in this context.

Like I said very partial.

• The number signs correspond to a numerical value in braille. The braille translates to "rot 15". Think about where to use rot 15. Oct 23 '18 at 19:03
• I fixed the binary conversion. Try to convert it again Oct 24 '18 at 0:23

The last equation is equal to

1

Because

It clearly says that 1=5 in the first statement, so 5=1.

I think that

the part saying that 5=z×z×4, since 4 is equal to 15, 15×z×z equals 5.

15÷5=4, so 4=z×z. 4=15,

so z= square root of 15

• Am I correct @Dandelion? If it is, I will leave this answer here in case the full answer is posted.
– user71418
Sep 22 '20 at 2:29
• If you click on Dandelion's picture, their profile says they haven't been on the site since February. Sep 22 '20 at 3:49
• At least, please give me a +1 if you agree
– user71418
Sep 22 '20 at 5:28
• I really don't understand what's going on here. Why is 15/5 = 4, and not 3? Why is 15=4? Where did "x=sqrt(15)" come from? Sep 22 '20 at 21:52
• It came from the lines themselves, though having 5=z*z*4 is harder to calculate
– user71418
Sep 23 '20 at 0:32