Securing Linux systems and applications; understanding Linux security features.

learn more… | top users | synonyms

1
vote
2answers
278 views

Linux kernel 3.2 syscalls

Just trying to get the assembler instructions for <__execve> of the code below because i want to build the shell spawn opcode list: #include <stdio.h> int main() { char *happy[2]; ...
6
votes
2answers
232 views

Process authentication for Linux

Is there any possibility to authenticate a running process in Linux to be sure that this is the original/right one? I know that an Linux operating system is only that secure like the way you use it. ...
0
votes
1answer
174 views

Different types of segmentation faults in Linux [closed]

In Linux, when the NX-bit triggers the segmentation fault seems to be "error 15", whereas a more typical error, such as attempting to read from invalid memory, results in "error 7", (seen from dmesg ...
5
votes
2answers
4k views

Pitfalls of SSD encryption

Encrypting an SSD is a process that is sometimes warned should be done with caution. E.g. http://en.gentoo-wiki.com/wiki/DM-Crypt_with_LUKS mentions how the SSD may keep hidden space used for wear ...
7
votes
2answers
686 views

Filling the disk with random data prior to encryption?

Filling the disk with random data prior to encrypting it will supposedly make it harder for the attacker to perform any cryptanalysis. Most sources seem to state this is because it will be harder for ...
11
votes
1answer
489 views

Slot machine segfault: what can we determine?

We walked into a casino and saw this near the entrance. I don't have a specific question, but is there anything that would be interesting to share and explain from the image?
4
votes
1answer
1k views

What tools can be use for Security Auditing for Redhat

Are there any good tools that can be used for Security auditing of Redhat Linux. That can audit all the critical areas of System and provide the detailed output of all the audited sections.
24
votes
4answers
11k views

What can an attacker do with Bluetooth and how should it be mitigated?

What are the security risks of Bluetooth and what technologies and best practices should be used to protect my device? What can an attacker do once a malicious device is paired with mine? ...
3
votes
2answers
893 views

Restarting nginx with Jenkins or Phing - is it safe to allow Jenkins to run sudo without prompt for password

I am implementing the recommendations from Integrating PHP projects with Jenkins for my own PHP projects. I have created a jenkins user in my ubuntu 12.10 server. I used Phing as my build tool and I ...
4
votes
4answers
536 views

What mechanism enforces user permissions in Unix/Linux?

One of the core pieces of security in Unix/Linux systems is limiting privileges by user. For instance, certain actions can only be done by the root user. In theory, this can keep a malicious process ...
0
votes
3answers
162 views

How to retrieve a site whose server is running Linux

I'm struggling to find a way to retrieve through Google a list of sites having Linux as their server operating system. Actually, I'd like to be able to test the following command: nmap -O ...
2
votes
2answers
201 views

Is it possible to boot into root's /bin/bash on a LUKS encrypted device?

I have to check the possibility of case mentioned in the title. An average Linux could be booted up into root's terminal directly without authentication by modifying kernel boot parameters. I'd like ...
7
votes
3answers
2k views

Security tradeoffs of pathname-based MAC (e.g., TOMOYO, grsecurity, AppArmor, …)

I have been learning about MAC (Mandatory Access Control) systems in Linux. Often, but not always, these are tied to Linux Security Modules. Some systems I've looked at: SELinux, Tomoyo, AppArmor, ...
3
votes
2answers
295 views

Safely remove an expired PGP key file

since it's possible to recover a deleted file I wonder how one can safely remove a PGP key file (with linux's command line tools) so that it's impossible to recover it. Maybe some dd command? Searched ...
2
votes
1answer
125 views

Trust linux images burned from untrusted systems

For securitys sake I'm assuming my system is successfully compromised after a targeted and/or non-targeted attack. I've downloaded some linux images and burned them to do a re-install. Since I can't ...
1
vote
1answer
109 views

How to forbid one directory only in TOMOYO (2.5)?

(For example) I want to restrict write access to /home/backup from anybody, except a particular backup script. (To protect from accidental deletion.) For this, I suppose, it is enough to have two ...
3
votes
1answer
215 views

“WICKED” entries in the default nginx vhost's logs

I have a small VPS running nginx, and for a long time now (several months, since I rented it) it has been collecting weird entries in its default (listen 80 default;) vhost's logs: 109.x.x.121 - - ...
3
votes
1answer
340 views

What are some steps to take for securing a Linux server that aren't in this list of obvious ones?

Obvious things: Disable root login (rather, don't enable it) Secure SSH (no root login, key auth only, timeout after inactivity, whitelist users who can SSH in, etc.) IP Tables firewall whitelisting ...
1
vote
3answers
203 views

Protect linux kiosk display

We use a small computer with linux attached to a big tv to display some data to the public. Normally, there is no keyboard connected. When a keyboard is connected at boot, we start the configuration ...
5
votes
5answers
576 views

HOWTO : Email encryption in a browser

I have read about encryption and I think it's a good idea for me to encrypt my email. I run ubuntu 12.10 and use Firefox for browsing. In my quest for learning how to use gmail/hotmail to send and ...
4
votes
2answers
1k views

Impact of Mathew Garrett's Secure GRUB Bootloader on UEFI Secure Boot

My eyebrows rose with Matthew Garrett announcing his Secure GRUB Bootloader less than three hours after no longer being a Red Hat employee. This work and its impact on the trust chain design of the ...
0
votes
1answer
246 views

SSH Log: “Accepted password for user…”

I have only port 29999 open for SSH connections. But in the log file I see entries like this: Accepted password for user1 from 190.101.200.100 port 55805 ssh2 saying that a connection was accepted ...
3
votes
1answer
463 views

How do I configure Terminal Server (and clients) for use over untrusted Wifi networks?

Suppose a client wants to directly connect to Terminal Server exposed to the Internet, without a VPN, ... what software & settings is needed to properly protect against WiFi based attacks? ...
12
votes
4answers
441 views

How to safely synchronize time over Internet?

All modern OS now keep accurate time by regularly synchronizing time over an untrusted network - Internet. Could an attacker conducting a MITM attack, influence or change the time of a computer while ...
11
votes
1answer
18k views

TCP Peer unexpectedly shrunk window messages in dmesg log

We get quite few messages like these in our dmesg log on various servers: TCP: Peer 0000:0000:0000:0000:0000:ffff:d431:5861:56369/80 unexpectedly shrunk window 2522304441:2522312601 (repaired) TCP: ...
2
votes
1answer
147 views

Why must VMX instructions trap?

What would happen if each of these instructions didn't trap into VMX root when executed in VMX non-root? INVEPT, INVVPID, VMCALL,VMCLEAR, VMLAUNCH, VMPTRLD, VMPTRST, VMREAD, VMRESUME, VMWRITE, ...
1
vote
2answers
232 views

What's the secure way to change UNIX permissions on a harcoded file often?

I'm writing a daemon that monitors something in the OS and flips execution permissions on a file in /run/ back and forth. The file has static contents and the file name is hardcoded in the daemon. I ...
2
votes
1answer
190 views

Consequences of using -s and -d arguments in iptables

We are studying iptables for a Computer Systems Security course. We are confused as to what happens when the -s and -d arguments are both used in the same rule, such as: iptables -A OUTPUT -s ...
3
votes
3answers
747 views

Online security check via command line

My scenario is that I have a VPS with Apache (mostly for development of my own projects) accessed via SSH; and I time to time I would like to do a quick check just to be sure that there's no potential ...
101
votes
8answers
5k views

Attacking an office printer?

I did an nmap scan on an advanced office printer that has a domain name and is accessible from outside the corporate network. Surprisingly I found many open ports like http:80, https:443, and ...
3
votes
2answers
859 views

Possible implementations of networked+encrypted filesystem

Is it possible to implement scheme where remote server just share its filesystem (or resizable container file in it) and it's locally encrypted and mounted? And what is best practical method? (On ...
3
votes
1answer
81 views

auditing mod security rule sets

Is there a audit system that can help me try my strings? Such as user agents, post/get data, a simple way to test general sql injections to see how my rule sets hold? I know with fire fox I can ...
1
vote
1answer
581 views

Why does the OpenSSH client on Mac OS X silently launch an ssh-agent for the user?

I'm confused by the difference in behavior of ssh clients I'm seeing on two different hosts. Just to be clear, this is the scenario: "macbox" OS X using OpenSSH_5.2p1 ssh client "sunbox" Solaris 10 ...
5
votes
2answers
1k views

How can I use nmap to distinguish between a normal linux machine and an android device?

According to this link: here, nmap 5.2 onwards is now supposed to detect android smartphones. I am using nmap 6.01 but it only identifies android devices as running a linux kernel.
3
votes
3answers
122 views

Can the root of a system access to unencrypted data when using a double tunnel?

I connect to a DMZ gateway system (B) which is not secured. From this machine (B) I can connect to the final destination (C). A-->B-->C I created a ssh tunnel from A to B and forwarding the port 22 ...
6
votes
3answers
5k views

What key does Linux use when storing user passwords?

Linux typically stores user names and password hashes in /etc/passwd or /etc/shadow. Now lets say I have an old CentOS distro and I want to attempt to recover a user's password (it's in a legal, ...
3
votes
1answer
148 views

Do public keys make Kerberos more secure (RFC4556)?

We're using IPA to centralize our authentication and I found an option to add a public key for each user. After doing a little research I found this to be an extension to Kerberos 5, RFC4556. From my ...
2
votes
1answer
993 views

Victim system's internet connection slow after ARP spoof?

I've been using Nemesis 1.4 to test ARP spoofing on a local victim machine. I've been spoofing both the victim machine and the default gateway to ARP redirect to my machine. Spoofing victim's source ...
0
votes
2answers
463 views

Any open source software firewall with country based ip blocking feature? [closed]

I am looking for an open source firewall with country based ip blocking feature for Linux OS.
6
votes
2answers
364 views

How a malware executes remote payload

Let's assume a malware was installed (on a UNIX-based platform) with some social engineering tricks. The original installed code itself may be benign, but the only malicious activity is that the ...
1
vote
2answers
333 views

Changing IP ID generation of a server

I've seen plenty about Idle Scans and incremental IP IDs on the net, but I have trouble finding a "solution" to the problem. Is there a way to "set" IP IDs for example to all zeros or is it coded into ...
3
votes
5answers
1k views

Security purpose of asking admin password to mount partition on Linux

So I divided my 250GB laptop drive into 2 partitions and some swap. On the second partition which is an ext4 60GB partition I installed Fedora 17. On the other bigger NTFS partition I've got Win XP ...
2
votes
1answer
520 views

Using mysql root account to execute root commands

Suppose that I have full root access to mysql databases, but not root user shell (linux). How can I use the full root access to mysql databases to execute root commands?
29
votes
3answers
55k views

What is the difference between authorized_key and known_host file for SSH?

I am learning basics of SSH protocol. I am confused between the contents of the following 2 files: ~/.ssh/authorized_keys: Holds a list of authorized public keys for servers. When the client ...
1
vote
1answer
2k views

NGINX / HTTP TRACE

I have a http server Nginx with HTTP TRACE Enabled. A single nmap --script=http-methods.nse host.name give this result : Not shown: 988 closed ports PORT STATE SERVICE VERSION [...] ...
1
vote
2answers
892 views

How to defeat ASLR in linux kernel? [duplicate]

Possible Duplicate: Stack Overflows - Defeating Canaries, ASLR, DEP, NX is there anyway to disable ASLR in Linux kernel 2.6.32-71.el6.x86_64, with Apache privileges?? I tried this commands: ...
7
votes
5answers
991 views

Securing Debian Apache PHP Server

I have Debian Apache PHP server. I want to secure him after the classic installation process. My usual steps are : List item update all packages remove all unnecessary services like named, portmap, ...
6
votes
2answers
1k views

Is privilege escalation possible when shell is under www user?

So, suppose that someone obtained a shell of a remote machine (of course via Internet). But the (linux) shell is under www user. Would there be any way of trying privilege escalation?
3
votes
2answers
3k views

How to hack linux via Local File Inclusion vulnerability?

During my penetration testing, I found a local file inclusion vulnerability. In fact this vulnerability existed in mailwatch <= 1.0.4, and its exploit existed in Exploit-DB. I tried to exploit the ...
3
votes
1answer
281 views

How to forward an specific FTP User to a Honeypot?

What I'm trying to do is to forward a specific FTP-User to a Honeypot, because the main server is for Shared Hosting and there's a lot of traffic, and I don't want to spend all the resources in ...