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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6
votes
2answers
264 views

How does getting a remote shell via exploiting a vulnerability really work?

I can understand what a buffer overflow is and that it allows you to write in places of the memory that you shouldn't be able to. I can also grasp the concept that there may be other software ...
2
votes
1answer
53 views

Prevent shell script inside image file

Recently, one of my website was hacked by someone who uploaded an image (shell.gif) to my server. I have put server side validation to check file extension + mime type of the image. However, they are ...
1
vote
2answers
85 views

Code Vulnerability in Shell script

I was given an assignment for my Computer Security class. We we were given a piece of code to analyze and determine the vulnerabilities that it might have. #!/bin/sh # shell script to create a copy ...
0
votes
0answers
48 views

Buffer overflow and register contents?

I am doing an exam practice question, suppose I have a function like; void func(char* arg) { char buf[32]; strcpy(buf, arg); } command break func: -buf begins at 0xbffebfb0 -(gdb) x/2wx ...
-2
votes
1answer
25 views

why the reverse_https payload runned at 0.0.0.0:443?

I created a reverse_https backdoor ( windows/meterpreter/reverse_https ) with msfpayload and then with multi handler want to create a reverse shell from my target , but when I exploited the handler I ...
0
votes
0answers
63 views

How does Metasploit's payload work with a remote target?

I have some simple questions. I often use Metasploit in my pentest engagements. It works fine when I'm inside a local network. Okay, we know that, when the payload is injected properly, it will give ...
1
vote
1answer
146 views

Possible shellcode mailed to me

When I opened my email this morning I found a rather odd message in my mail box. It didn't seem like your every day spam email as it looked like a base64 encoded string and nothing else. Here is a ...
1
vote
0answers
58 views

What exactly is shellcode? [closed]

What is shellcode and how does it work? I used to think it was just a binary string encoded with hex, but I recently started reading more and it seems it is something completely different. I know it ...
0
votes
1answer
127 views

How does the NOP sled work with MSFVenom? [closed]

I'm generating payloads with MSFVenom and here's a sample output: user@localhost:~ $ msfvenom -p windows/shell_bind_tcp -b '\x00\x0a\x0d\x20' -i 3 -n 200 -f python No platform was selected, choosing ...
1
vote
0answers
32 views

unable to execute shellcode,which is place on stack [duplicate]

I am trying to execute the shellcode to spawn an "sh" shell. I have taken shellcode as command line arguement,copied it to stack and tried to overwrite the return address of main function with the ...
0
votes
1answer
50 views

Intercept Android's http/https traffic with shell access [closed]

Assuming you have a shell access on a rooted Android device. Let's say the shell was given upon an exploitation, eg. Android Webview vulnerability. The question is what is the best way to intercept ...
19
votes
8answers
2k views

PHP malware/shell keeps resurrecting [duplicate]

So I've been fighting this problem for months now and decided that it's beyond my limited (if at all) server skills, and that I need help from the pros. I have a VPS (with root access) which hosts ...
0
votes
0answers
25 views

Execute form environmental variable while stack is not executable

Strange thing happened. I created EGG=NOPs + shellcode. Then i get the address of EGG; I made buffer overflow and jumped to it and get the shell(address of shell is the second parametr). How is this ...
1
vote
1answer
136 views

MySQL vs MSSQL injection to shell uploading

What is the difference between uploading a shell via sqli in mysql vs mssql?
0
votes
2answers
90 views

Safe to use setuid with absolutely no input?

I have a shell script which syncs some files from a remote source and I have a pretty typical HTTP server set-up. There is a user who owns the files served by the HTTP server and a user which runs the ...
-1
votes
2answers
119 views

Cannot get simple shellcode runner to work [closed]

I'm just trying to execute shellcode directly from the command line. I send a simple 0x90 NOP and get a segmentation fault? root@server:~# gcc shellcode.c -o shellrun -fno-stack-protector -z ...
1
vote
1answer
203 views

Program exiting after executing int 0x80 instruction when running shellcode

In school I was given an assignment to perform a buffer overflow, which would execute some shellcode and open a new shell. After a bit of fiddling the buffer overflow succeeded, and when I ran the ...
0
votes
1answer
187 views

Backdoor under Akismet wordpress plugin

my site recently got hacked or my users leaked out their passwords. The hacker install this plugin with a shell or backdoor in it. The file name is the "honda.zip" and inside is some Akismet plugin's ...
-1
votes
1answer
98 views

Why should I use ROP for exploit dev? [closed]

Return Oriented Programming is a technique for bypassing DEP which based on ret2libc.. ROP is used for formatting the API function parameters in order to make a reliable shellcode.. I dont get ...
2
votes
1answer
88 views

Are stack buffer overflows even possible in this instance?

Let's say there is a C program that simply takes a string argv[1] and uses sprintf to copy it in a finite buffer. Classic stack buffer overflow. Let's even say the program is more complicated, ...
0
votes
1answer
157 views

Are shell scripts / bash inherently less secure than other (script) languages such as python?

Are shell scripts / bash suitable for any kind of task as long as the developer(s) write correct, security bug free scripts? Or are shell scripts / bash less advisable for some tasks such as parsing ...
0
votes
1answer
187 views

Execute a remote PHP shell which is inside a file I dont have permission to access

Hi need some help here. I am trying to exploit an unsanitized file upload with a PHP backdoor. Basically the file uploads successfully and I can see my backdoor inside the web applications /images/ ...
0
votes
1answer
234 views

Which shell is more secure, mksh or bash?

Which shell is more secure, mksh or bash? There has been some discussion pointing into the direction, that mksh is more secure. How to come to that conclusion? By looking which code was more audited ...
2
votes
2answers
347 views

PHP shellcode inside /tmp. Is the server compromised?

I have a Debian 7 VPS that runs Nginx, PHP5-FPM and MariaDB. This server runs a couple of WordPress installations, phpMyAdmin and Roundcube Webmail. One is my personal blog running WP 3.9.1 and ...
1
vote
1answer
304 views

Metasploit generating strange shellcode

So I just used metasploit to generate the payload/linux/x86/shell_bind_tcp payload without null bytes (generate -t raw -b '\x00' -f shellcode). Here's the shellcode: $ xxd -p shellcode ...
3
votes
1answer
123 views

msfvenom -b flag not working?

When using msfvenom, I am under the assumption that the following syntax should give me shellcode without \x00 \x0a \x0d or \x40, because of the -b option msfvenom -p windows/shell/bind_tcp -b ...
0
votes
2answers
729 views

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 ...
1
vote
2answers
87 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 ...
1
vote
3answers
356 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 ...
2
votes
1answer
625 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 ...
1
vote
1answer
299 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 ...
0
votes
1answer
105 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
votes
2answers
1k 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 ...
1
vote
2answers
247 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 ...
1
vote
1answer
1k 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) { ...
0
votes
1answer
1k 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
votes
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 ...
2
votes
3answers
1k 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, ...
6
votes
3answers
336 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 ...
2
votes
2answers
2k 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 ...
21
votes
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 ...
4
votes
3answers
701 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 ...
9
votes
1answer
1k 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 ...
4
votes
2answers
892 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
146 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
266 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
534 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
555 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
663 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
213 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 ...