Once we put together the rest of the kernel module (Ftrace, etc), we can build it and try it out. This might seem like a simple technique to pull off, but its only because were repurposing two different syscall hooks that weve already covered: sys_kill() in Part 3 and sys_getdents()/sys_getdents64() in Part 6. "Used" memory in top larger than the VmSize of all pocesses listed in /proc/? I did the following, to put the process name (the process that I'm trying to hide) into the buf, then use copy_from_user() to copy it into the kernel space. unhide proc or unhide-linux26 proc for a 64bit system. It should be clear what the new parts are doing (look for the comments), but if not, try re-reading the paragraph above it. This function override sys_call_table [__NR_write]. Would it be illegal for me to act as a Civillian Traffic Enforcer? Its worth pointing out that the file is still there and you can go ahead and open it, delete it, etc without any trouble, but dont expect it to show up in ls! To remove a rootkit, it is often necessary to reinstall the operating system. In particular, we see that its got two interesting fields; d_reclen and d_name. It is impossible to hide the process unless one starts messing around in the kernel to limit this. This is because strlen(hide_pid) will be 0, so the call to memcmp() will always return true. . kandi ratings - Low support, No Bugs, No Vulnerabilities. Linux Rootkits One way an intruder can maintain access to a compromised system is by installing a rootkit. Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, Which kernel version are you running? Making location easier for developers with new data primitives, Stop requiring only one assertion per unit test: Multiple assertions are fine, Mobile app infrastructure being decommissioned. # linux # rootkit # stealth # processes Now that we know how to hide directories (see last time ), we can also hide processes! The first is the record length and is the total size of the struct in bytes. Are Githyanki under Nondetection all the time? We can check this by looking at the output of strace -e openat ps or strace -e openat top. We can see sys_getdents64 being called with all its arguments and that its written 600 bytes into the buffer we provided. It would probably be a good thing to install and run rkhunter. Rootkits; Scenario. Memory rootkits hide in the RAM memory of your computer. Not only can Sandfly decloak hidden PIDs, but we also can detect cloaked data in files, cloaked directories and more. Horror story: only people who smoke could see some monsters, Best way to get consistent results when baking a purposely underbaked mud cake. serveral tips: pathname is from user space, thus copy_from_user magic is required; function type must be long, ive tried int, it returns UINT_MAX - 2 instead of -2 (-ENOENT) To learn more, see our tips on writing great answers. Rootkits are, according to their type, unable to spread by themselves. Hiding Processes - LINUX task_array PID Process 0 As LKM rootktis are based on common hiding tactics, the currently released tool will work against a variety of rootkits deploying similar hiding techniques. Now the file of interest in the entire rootkit is /lib/libcurl.so.2.17..This file being referenced in /etc/ld.so.preload means that it is the one that is intercepting system calls to do the grunt work of the rootkit to hide. We do further checks in critical system areas for files loading kernel modules but are hiding this data from view. Stack Overflow for Teams is moving to its own domain! Is my understanding is correct? Process won't show in the process list. How to draw a grid of grids-with-polygons? Furthermore, the process to hide can be selected after authenticating with the rootkit . The rough outline of our hook will look like this: Hopefully by this point, the above skeleton makes perfect sense. Looking back at include/linux/readdir.c we can see d_reclen used in precisely this way (albeit after being copied into another struct first). How do I programmatically determine operating system in Java? Features Hide process Hide process CPU usage Hide files that his filename starts with the MAGIC_PREFIX Rootkit installation Build $ git clone https://github.com/alfonmga/hiding-cryptominers-linux-rootkit $ cd hiding-cryptominers-linux-rootkit/ $ make Loading LKM: Most rootkits/malware use the power of the kernel to hide, they are only visible from within the kernel. Rootkits can modify system files to give the hacker access to sensitive information or disable security features. I prefer women who cook good food, who speak three languages, and who go mountain hiking - what if it is a woman who only has one of the attributes? Therefore, they are spread by the attacker by such tactics that the user is unable to notice that something is wrong with the system. Let's look in /proc/1431 to obtain more information about the . It might be that OSSEC is using the unhide utility to check for hidden processes. Is my understanding is correct? This gives us two results, as mentioned earlier; one for 32-bit and another for 64-bit. Simply build and run sandfly-processdecloak for your preferred Linux platform using the built in scripts. In the full rookit (on the repo), there are four hooks in total: one each for sys_getdents and sys_getdents64 as well as another two for the pt_regs and old-fashioned calling convention for each of those. Rootkits are collection of tools that are used to provide backdoor access for Trojan horses by modifying important system files. Now that we know how to hide directories (see last time), we can also hide processes! I check the content of buf. using copy_from_user(), buf is copied into a kernel buffer kbuf and then upon detecting the ps||pstree|| command using strstr(), it looks for the process_to_hide(H4X0R). This hides process from all other commands such as ps, top, htop . @perplex I meant the other way; I think your kernel is too recent; you might need an older one for kbeast. According . A rootkit contains a set of tools and replacement executables for many of the operating system's critical components, used to hide evidence of the attacker's presence and to give the attacker backdoor access to the At this point, weve used several different techniques to manipulate the kernel into doing interesting things. Sandfly uses a variety of methods to detect and decloak LKM style rootkits in more extensive ways than this free tool does. My understanding is *buf, contain the name of the process it is trying to hide. Be warned though, its not as simple as it may sound! https://github.com/dsmatter/brootus bROOTus is a Linux kernel rootkit that comes as a single LKM (Loadable Kernel Module) and it is totally restricted to kernel 2.6.32. https://github.com/jarun/keysniffer A Linux kernel module to grab keys pressed in the keyboard. This tool sometimes raises false-positives. Making statements based on opinion; back them up with references or personal experience. The tool leverages a Process ID (PID) bruteforce tactic to find processes that are not showing themselves in the standard /proc directory listing on Linux. Is Committed_AS in /proc/meminfo really the correct number for allocated virtual memory in Linux? To do this, we need yet another linux_dirent64 struct, which we'll call previous_dir, and update it as we loop through everything. To do this, we need yet another linux_dirent64 struct, which well call previous_dir, and update it as we loop through everything. This is because nearly all userspace tools that give us information about processes just read the contents of the /proc/ filesystem. Could a translation error lead to squares to not be considered as rectangles? We can check this by looking at the output of strace -e openat ps or strace -e openat top. The only gotcha is what to do when there is no previous entry, i.e. The description of the project says "An LKM rootkit targeting Linux 2.6/3.x on x86(_64), and ARM". The best answers are voted up and rise to the top, Start here for a quick overview of the site, Detailed answers to any questions you might have, Discuss the workings and policies of this site, Learn more about Stack Overflow the company, How to view linux hidden process and remove rootkit, Making location easier for developers with new data primitives, Stop requiring only one assertion per unit test: Multiple assertions are fine, Mobile app infrastructure being decommissioned. Are there small citation mistakes in published papers and how serious are they? Hope you enjoyed working through this one - Well Done for making to the end! To do this, well use memmove(), but we also have to remember to decrease ret by d_reclen too so that we dont run over the end of the buffer as we loop through the rest. The trick will be how we find any entries that start with our chosen prefix string, as well as how we trick the system into skipping these entries once weve found them. How to list hidden file/process/regKeys by rootkit, Rootkit attack by inserting new binary formats. 6. The last thing we need to figure out is how to get the system to skip over any entries we find that start with our prefix boogaloo. Do you see that hidden process every time you run OSSEC? Making statements based on opinion; back them up with references or personal experience. Were going to combine a few of these techniques now in order to hide certain files and directories from userspace. Connect and share knowledge within a single location that is structured and easy to search. Its only slightly different from where we started in Part 5, but in that case the only fiddling we did was overwrite the kernel buffer with 0x00 before copying it back to userspace. A rootkit is a group of software tools used by an attacker to cover his or her tracks. A computer system or a computer network can be infected with Trojan . The Trojan from last year called Hand of Thief failed in its ambitions to be the first banking Trojan for Linux desktops. Here is the definition from fs/readdir.c if youre trying to work it out yourself without peeking at my version: Lets take a look at what happens when we go ahead and load this rootkit after creating a file that wed like to hide. Linux LKM Rootkit Tutorial | How To Protect Yourself From MALICIOUS LKM Rootkits | Part 3 - I show you two programs rkhunter, and chkrootkit that can help y. 1. The trick that we are going to use is to increment the d_reclen field of the entry before the one we want to hide by the d_reclen value of the boogaloo entry. I'm trying to learn how rootkit works (for educational purposes). Because we are an agentless product, we are able to get onto a large number of Linux hosts to investigate them for LKM rootkits without any system impacts or risks to system stability. How can we create psychedelic experiences for healthy people without drugs? Is it OK to check indirectly in a Bash if statement for exit codes if they are multiple? You can use unhide or tool such as rkhunter to scan for rootkits, backdoors, and possible local exploits. Instead, rootkits actually depend on that attacker/malicious user already has already exploited the target and gained root . See examples below. If you are using Linux kernel version 3.2+ (or RHEL/CentOS v6.5+ above) you can hide process from other users. as for procfs, addtional check is needed, everthing under our hidden /proc/PID should be hidden too. This is because nearly all userspace tools that give us information about processes just read the contents of the /proc/ filesystem. Its still in the kernel, but because its not in the headers, your module will fail to build. Freeze and unfreeze processes transparently? By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Does activating the pump in a vacuum chamber produce movement of the air inside? In their hopes to move away from 32-bit systems, the kernel developers removed the definition of linux_dirent (note the absense of 64) from the kernel headers. There is a slight caveat that we will hide all files or directories with the name of the PID were hiding. Memory rootkit. PID 43218 gets hidden from the output of ps - and we didnt even have to try that hard! LO Writer: Easiest way to put line of words into table as rows (list), Book where a girl living with an older relative discovers she's a robot, Including page number for each page in QGIS Print Layout. Process '2517' hidden from /proc. Rootkits can launch hidden processes that consume resources or run malicious code. I've a working code that looks like original Kbeast code. At this point, we realise that well have to allocate our own buffer into kernel space, modify it there and then copy it back (just like in Part 5). I and just installed OSSEC and it is telling this. This is quite an old exploit (2011), and hasn't likely functioned for quite a while. "The rootkit hooks the readdir and readdir64 . This article introduces an unconventional method to hide Linux process from users, with only one line of code: Modify the pid of the process. * hide_pid will store the string representation of the PID we're hiding, * Declaration for the real sys_kill() function, * Pull out the arguments we need from the pt_regs struct, * If the signal is 64, then print a message to the kernel buffer and, * Otherwise, just return the real sys_kill, /* Hide the directory with name in hide_pid */, Privileged Container Escapes with Kernel Modules. How to constrain regression coefficients to be proportional. The syscall reference directs us to fs/readdir.c, where we find the definition for sys_getdents64. Then well set current_dir = dirent_ker + offset. to get a file descriptor (3), # Check the directory pointed to by file descriptor 3 exists, # Call getdents64 syscall with the file descriptor and a pointer to userspace, /* Pull the userspace dirent struct out of pt_regs */, /* Declare our kernel version of the buffer that we'll copy into */, /* Call the real getdents64, and allocate ourselves a kernel buffer */, /* Check that neither of the above failed */, /* Copy from the userspace buffer dirent, to our kernel buffer dirent_ker */, /* Copy dirent_ker back to userspace dirent */, /* Declare current_dir pointer and the offset variable */, * Note that we have to cast dirent_ker to (void *) so that we can add, /* Compare the first bytes of current_dir->d_name to PREFIX */, /* Increment offset by current_dir->d_reclen so that we iterate over, /* Declare the previous_dir struct for book-keeping */, /* Check for the special case when we need to hide the first entry */, /* Decrement ret and shift all the structs up in memory */, /* Hide the secret entry by incrementing d_reclen of previous_dir by, * that of the entry we want to hide - effectively "swallowing" it, /* Set previous_dir to current_dir before looping where current_dir, Privileged Container Escapes with Kernel Modules, Linux Rootkits Part 5: Hiding Kernel Modules from Userspace, Linux Rootkits Part 6: Hiding Directories.
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