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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Can pipe | shell | nc > pipe achieve remote shell?

In one of the articles I have came across an exploit of Dell devices that said when you trigger the following line of code (executed somewhere in php) you will get a remote root shell : mkfifo ...
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2answers
47 views

Detect blocked reverse shell

I am wondering if there is a way to detect if a reverse shell is blocked by egress filtering or an obligatory proxy, or the exploit just failed. I am asking this question in the context of a SE media ...
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3answers
86 views

Documentation on Meterpreter Shells

I've been looking for some decent documentation on Meterpreter shells, but I can't seem to find anything useful. I would like to know when to use what kind of shell for a certain situation. All I ...
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1answer
70 views

Clamav can't detect encoded virus files

I have a PHP sheller file (like c99 file) but it's Encoded ( with this functions: eval(gzinflate(base64_decode("7P3rehblahblah)) ) and the clamav virus scan can't detect it. How i can detect virus ...
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1answer
142 views

How to deny shell execution in all sub-directories?

I want nginx to deny users who have folders inside /webroot/uploads e.g. /webroot/uploads/user1 /webroot/uploads/user2 /webroot/uploads/user999 to execute any shell (php, pl, py, binary). The ...
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1answer
83 views

How to find malicious images in server?

Recently my Drupal site on a Linux server has been targeted by session hijacking attacks. I guess the attacks were originated from images containing malicious code which where uploaded to the web root ...
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2answers
185 views

NX bit: does it protect the stack?

I once heard the NX bit was a panacea, then that it was not. One detail I've wondered about though: Does the NX (no execute) bit protect against code inserted into the stack and executed there? It ...
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2answers
121 views

How do arbitrary payloads execute on the remote machine?

I understand executing something like a reverse TCP bind via shell relies on resources being available on the victim machine... and in the case of running a, shall we say, Ruby script from the command ...
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1answer
293 views

Starting a new shell in a strcpy exploit using buffer overflow

I'm learning about buffer overflows and have this vulnerable code which I'm trying to start a shell from: #include <string.h> void myfunction(char *arg); int main(int argc, char **argv) { ...
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1answer
236 views

Stack buffer overflow confusion

I am trying to dig deeper into the nuts and bolts a stack buffer overflow using the classical NOP-sled technique. Reading some articles and watching videos brought me to a confusion which can be ...
18
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1answer
1k views

Could someone explain parts of the FBI's Firefox 0-day?

Here is the full Javascript (and related iframes) that the FBI apparently injected into all "Freedom Hosting" pages in the course of their recent takedown. http://pastebin.mozilla.org/2776374 The ...
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3answers
334 views

How to determine the size of payloads available in MetaSploit

I've noticed that there are a lot of different payloads to choose from in MetaSploit, and the choice (assuming there's enough room in the target) usually depends on what you're trying to do. However, ...
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3answers
197 views

Buffer overflow stack adjustment

I am quite new to buffer overflows and I am practicing right now different types of buffer overflow attacks. the shellcode was not executed until it was padded with NOPs although its set properly in ...
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2answers
450 views

How to deal with MySQL's Errcode 13 when trying to write a shell

My attack machine is running Kali and the server is running CentOS 6.4 with DVWA. I'm trying to write a shell through an SQL injection. The payload is ' UNION SELECT '', '<?PHP ...
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2answers
2k views

Is it possible to write shellcode in C++?

Usually I write assembly programs and then dump their contents to get the shellcode. What I was wondering is whether I could write a C++ program instead of assembly, then dump and use that instead of ...
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3answers
475 views

Is writing shellcode still a valid skill to have/learn?

Following up from this question: Should I bother teaching buffer overflows any more? I am a it sec researcher and also security course instructor. Recently questions have been raised about the ...
8
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1answer
453 views

NOPS in Metasploit

Problem I do not know what a "NOP" is in Metasploit Framework or otherwise. What I do know MS Unleashed says, "Nops keep the payload sizes consistent." A few question posts mention buffer ...
3
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2answers
518 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 ...
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1answer
133 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 ...
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1answer
129 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 ...
3
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1answer
316 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
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1answer
412 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
374 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, ...
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1answer
176 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 ...
3
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1answer
235 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 ...
3
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2answers
630 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
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2answers
3k 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 ...
2
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1answer
1k 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
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1answer
253 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
511 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
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3answers
561 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
335 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
1k 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 ...
26
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2answers
6k 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?