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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2answers
141 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 ...
2
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3answers
620 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 ...
1
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1answer
395 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 ...
3
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1answer
1k 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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2answers
367 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
115 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 ...
2
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2answers
2k 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 ...
18
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1answer
2k 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 ...
0
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1answer
2k 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 ...
7
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3answers
419 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 ...
21
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2answers
3k 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 ...
2
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2answers
3k 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 ...
8
votes
1answer
710 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 ...
4
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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 ...
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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
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1answer
352 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
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1answer
685 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. ...
4
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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 ...
3
votes
1answer
949 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
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1answer
244 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
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1answer
480 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
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 ...
4
votes
2answers
2k 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
11
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2answers
9k 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
votes
1answer
386 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 ...
6
votes
3answers
1k 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 ...
3
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2answers
2k 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.
2
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1answer
859 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 ...