In computer security, a shellcode is a small piece of code used as the payload in the exploitation of a software vulnerability. It is called "shellcode" because it typically starts a command shell from which the attacker can control the compromised machine, but any piece of code that performs a ...

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4
votes
2answers
1k views

ASLR and how a program can actually call its functions

I'm studying protection techniques and I've got a doubt about how ASLR works for a program in a Windows environment. As far as I know ASLR works by randomizing part of the imagebase address when ...
-1
votes
1answer
147 views

E-mail with obfuscated code / no trace in e-mail server

I've got a situation where one of my clients sent me an e-mail with what appears to be obfuscated shell code. The really bizarre thing here is that I see no trace of this e-mail showing up in the mail ...
0
votes
1answer
295 views

Shellcode Segfault mid execution?

In doing a university assignment, we are launching a shell on a remote server. That's all fine, I have connect back shell code, and when I hardcode the hex attack string into the server and jump to ...
4
votes
1answer
570 views

NX bit causes segfault on NOP slide?

doing an assignment for university. We have to exec a shell on a remote server. We're told the NX bit is not set, however, when we redirect to our injected code, the server has a segmentation fault. ...
8
votes
1answer
631 views

Better way to import Win32 APIs from injected shellcode

I'm injecting native x86 code into a .NET application, via a TLS callback in the binary image. Unfortunately, .NET executables only import mscorlib.dll within the PE, and have kernel32.dll mapped ...
2
votes
1answer
798 views

SafeSEH and x64

I read here that /SAFESEH is only valid when linking for x86 targets. /SAFESEH is not supported for platforms that already have the exception handlers noted. For example, on x64 and Itanium, ...
0
votes
1answer
226 views

Does filtering HTML syntax prevent a web shell from being dropped through a textbox? [closed]

I have an admin panel that is running off a mysql db. On that panel, I have text boxes that allow an "Admin" to input plain text OR HTML Styling that will be displayed on a section of the site that is ...
5
votes
1answer
409 views

Stack canaries protection and ROP

As far as I know stack canaries are values written on the stack that, if overwritten by a buffer overflow, force the application to close at return. My question is: if I overwrite both EIP and stack ...
4
votes
2answers
1k views

Do I always have to overwrite EIP to get to write on the stack in a buffer overflow?

Do I always have to overwrite EIP to get to write on the stack in a buffer overflow? How's the memory organized? I can't find a proper graph with google
10
votes
2answers
7k views

How “leaking pointers” to bypass DEP/ASLR works

I was wondering if anyone could give me some clues on how "leaking pointers" to bypass DEP/ASLR work. I read here: The only way to reliably bypass DEP and ASLR is through an pointer leak. This ...
3
votes
1answer
2k views

Stack smashing keep getting segmentation fault

I have a homework assignment to do stack smashing, The exploit code creates a badfile in which the vulnerable file reads and buffer over flow occurs. I have already did the 2 commands below to ...
2
votes
1answer
350 views

How to achieve interactive shell attack?

Usually when a person gets a shell by attacking some vulnerabilities, what a person gets is non-interactive shell. So when I call FTP interactive client, shell fails. Is there any way I can do ...
3
votes
2answers
1k views

Shellcode that is smaller than 295 bytes that spawns a shell [closed]

Metasploit payloads produce more than 300-byte shellcodes. But I want my shell-spawning shellcodes to be less than 295 bytes. Can anyone show me the links to these shellcodes? Thanks.
6
votes
3answers
951 views

What methodologies are useful when reverse-engineering malware / shellcode?

Whilst I'm familiar with reverse engineering techniques from a technical standpoint, I've never found a good methodology for approaching and dissecting malware / shellcode. I've found hundreds of ...
2
votes
1answer
731 views

What tricks can be used to prevent debugging?

What tricks can be used to prevent or hinder debugging? Examples: IsDebuggerPresent API on Windows Exception handlers used for program flow. GetTickCount / rdtsc checks. Are there any good ...
4
votes
3answers
2k views

Are there any tools that focus on shellcode analysis?

Shellcode presents certain challenges for disassembly. It often self-modifies, jumps to the stack (where the shellcode will likely be placed), and relies on certain unusual tricks that standard ...
36
votes
2answers
18k views

How do ASLR and DEP work?

How do Address Space Layout Randomisation (ASLR) and Data Execution Prevention (DEP) work, in terms of preventing vulnerabilities from being exploited? Can they be bypassed?