Content related to computer security., i.e. content about policies, mechanisms, etc. needed make sure data is not leaked or corrupted and services available in all circumstances.

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3
votes
2answers
7k views

Disable stack protection on Ubuntu for buffer overflow without C compiler flags

I'd like to try some shell codes and I want to disable linux protections. I know I could compile using flags but I know another way exists to disable these protections in general I just can't ...
-3
votes
1answer
183 views

Priviledge separation for Firefox (aka: how to secure webbrowsing)

I do this on Scientific Linux 6.3 (to implement it, it requires a minimal Linux knowledge): Shared directory for downloads Remember you can only copy from or to this directory, never "move" files ...
2
votes
2answers
182 views

Do I need to remove all “java|jre” packages from my system to be secure from java vulnerabilities?

Currently I have these installed on my Scientific Linux 6.3: [root@localhost ~]# rpm -qa | egrep -i 'java|jre' java-1.7.0-openjdk-1.7.0.9-2.3.7.1.el6_3.x86_64 ...
3
votes
1answer
315 views

Is running programs as another user useful?

After watching a talk by Douglas Crockford on security where he talks about how browsers got the right answer to the question "Who's interest does the program represent?", I wondered if it was ...
5
votes
1answer
233 views

Why Nmap fragmented scan on Linux is only working from virtual environment?

OLD QUESTION AND TITLE (Look further down for the updated question): Why Nmap fragmented scan is only working on Backtrack? I spent quite a few hours today trying to capture and study some ...
4
votes
3answers
977 views

Is a command's stdout to the terminal being logged?

I am interested in learning whether a command's output to the terminal is logged somewhere. Since that can be a bit too generic, what about cat (and ccat) in specific? If I use cat on a file, will ...
2
votes
1answer
232 views

Port 110 visible to the outside world - necessary or a bad idea?

I just did [a test][1] that told me my gateway's (debian squeeze) port 110 is visible from outside. It's a box with two network cards, eth0 is for my internal network (192.168.1.0/24) and eth1 goes ...
1
vote
1answer
234 views

Ping from Outside: How do I make my system invisible?

I just did a test that told me my gateway (debian squeeze) responds when being pinged from outside. It's a box with two network cards, eth0 is for my internal network (192.168.1.0/24) and eth1 goes ...
15
votes
1answer
24k views

Is it okay to disable requiretty?

I'm trying to set up a deploy script using Capistrano At a step cap deploy:setup script is connecting to my server and trying to run commands that create directories. Then I see an error: msudo: ...
22
votes
4answers
1k views

Is there any way attacker could use mkdir to compromise a system?

I'm setting up a restricted user account for user ricardo, a troublesome user on my system. I want to grant him the right to make directories using sudo, which he sometimes needs to do. I'm ...
3
votes
1answer
76 views

Change order of Private Keys passed via SSH login

ssh -i ~/.ssh/username username@xx.xx.xx.xxx -v Server is set to accept only 3 log on tries. The ssh system is trying 3 identity files before attempting the correct identity file. debug2: key: ...
2
votes
2answers
733 views

setuid programs don't seem to run setuid in TinyCore Linux

I want to demonstrate the vulnerability of setuid programs using the TinyCore Linux live cd. That is, I craft a special program, with special permissions, so that it runs as the owner of the file ...
2
votes
1answer
535 views

Setting the root password vs. sudo -i

Should one always set a root password, or is sudo -i acceptable? Two problems is in reading other posts (maybe junk I realize): sudo -i eliminates the need for a password. Isn't that a problem for ...
1
vote
2answers
141 views

understanding how to run script securely as limited user

I'm a long time dev but linux newbie. I've been building this (http://tryperl.com) to learn linux. So, my question is just about some *nix stuff I don't fully grok. One of the things I want to do is ...
2
votes
1answer
760 views

Properly Set Permission to /home/user folder for webserver

I'm currently setting up my own Linux server running CentOs 6. To test the security on my server I wrote a PHP script that acts like a sort of "navigator". I can go one directory up, open the files, ...
4
votes
2answers
2k views

Purpose of using setuid() in SUID programs

I wonder that an SUID program like passwd is using the setuid() function call. Why does it drop root privileges? Against what types of attack does this help? Buffer-overflow?
1
vote
3answers
1k views

SUID permissions - Which is correct?

Trying to secure a Linux server and have little experience with SUID. After executing find / -perm +4000 many programs were discovered. I have seen conflicting advice here and hereon what should ...
8
votes
9answers
2k views

How to prevent a process from writing files

I want to run a command on Linux in a way that it cannot create or open any files to write. It should still be able to read files as normal (so an empty chroot is not an option), and still be able to ...
5
votes
2answers
6k views

what is OS hardening in linux or unix?

The term OS hardening itself is misleading/vague to me as i am reading to understand it online here. It seems to me that its something related to making linux/unix box more secure.
1
vote
2answers
93 views

how to require sudo to view files?

I have a ssh server. I allow people to connect to it if they want. I do my programming homework on it. I am in trouble with my teacher because people were cheating off it. I need to know how to ...
3
votes
1answer
2k views

Apache boot without asking for passwd

So I'm maintaining a server which has a verified SSL certificate setup, however there is a password on the private key and so whenever apache is reboot, we get a message asking for the password. This ...
1
vote
2answers
5k views

iptables blocking from internet side on eth1?

How to use iptables to deal with two Ethernet ports? eth0 port for LAN use (192.168.1.50 Private IP). eth1 port is connected to the internet via cable modem (80.0.xxx.xxx public IP). ifconfig ...
1
vote
2answers
71 views

What permissions should I set if I'm the only user?

I'm the only user on a OS X machine and am wondering what the best practice is for setting permissions on my sensitive files. Specifically, are there reasons to prefer one of the following -rw------- ...
1
vote
3answers
404 views

Can a mounted encrypted filesystem be safe from root?

I have access to a shared remote computer from which I would like to run some code I have written which uses an interpreter (not a compiled code). I would like to protect this source code from other ...
13
votes
2answers
511 views

How can I be sure that a directory or file is actually deleted?

I know that most files, when deleted, aren't actually removed from the disk, and can be recovered later. How can I ensure that a directory I had deleted will actually be removed from the disk? Are ...
1
vote
0answers
129 views

Deny/allow a user's access to a port dynamically

I have stumbled upon this little tech dilemma yesterday, and know that there is a solution to it (IRC BNC resellers have it implemented already). However, the exact details and implementation elude ...
6
votes
2answers
705 views

Can a user brute-force a directory listing without having read permission on the directory?

I noticed that when a user is working in a directory to which he does not have read permission that using cd produces different error messages, depending on whether or not a subdirectory exists: $ ls ...
5
votes
3answers
294 views

Creating linux distro for use during exam

I'm thinking about creating a liveCD having some linux on it. The distro (let's call it Exam OS) is meant to be used by students during an exam and should be, at least, unpleasent to bypass. Let's ...
17
votes
3answers
2k views

Securely delete files on btrfs filesystem

Sometimes, there's the need to delete a file in a filesystem, and make sure that the file is truly gone. A file that contains sensitive passwords, for example, should be throughly wiped from the disk. ...
5
votes
2answers
125 views

Is it more dangerous to connect to the net as root?

If I make some kind of tcp connection to the net as root, is that less safe then making the same tcp connection as a normal user? I have been suspecting for a while that by making a connection as ...
9
votes
1answer
3k views

How to stop users from Switching to Root user

I have disabled the root user login from Sshd.conf file so now no one can login using root user even if they know the password SOMEHOW. Now I have 3 users in server ROOT,EMERG and ORACLE. I want to ...
2
votes
1answer
514 views

Running a local port scan and found open ports but, don't know what they're used for?

I wrote a very basic python script to port scan my system. I'm running linux-mint lisa: open_ports = [] for port in xrange(65536): conn = socket.socket(socket.AF_INET, socket.SOCK_STREAM) ...
5
votes
1answer
692 views

What should I check after an unauthorized access?

I accidentally left an open port on my router, leaving access to one of my computers via SSH, using a rather insecure password. I noticed because I checked /var/log/auth.log and there is just one ...
1
vote
3answers
64 views

execute file in server more safely?

We have a application which takes a C++, C, or Java file as input, executes it, and displays the output to the client. What are the best measures that can be taken so that no security related issues ...
5
votes
3answers
715 views

Why does time/ident/daytime/comsat run after an OpenBSD 5.2 install?

I installed an OpenBSD 5.2 using "-* & +etc* & +base* & +bsd". After finished with the install, I rebooted, then netstat -at | grep LISTEN, this is what I get for output: Why does so ...
9
votes
1answer
945 views

How can I limit ssh *remote* port forwarding?

I need to limit which ports can be remotely 'ssh -R' forwarded by an user. I know about permitopen option on authorized_keys, but as it says on man page it only limits local 'ssh -L' port forwarding ...
4
votes
3answers
2k views

Is it impossible to run as `root` if the machine isn't rooted?

By default, the user of the device does not have access to certain root objects (e.g. the /data directory). Even though these objects are off-limits, however, it would seem to me that these objects ...
4
votes
2answers
586 views

How to lock a directory?

I want to block any kind of access to a certain directory unless a password is provided. It could be my root or account password. The directory is residing on an NTFS partition, and this method needs ...
0
votes
0answers
54 views

Ossec Installation Error

While installing Ossec Hids 2.6 on Redhat 5.5 installed on Virtual Machine, I got this error message. Whats wrong here.
1
vote
1answer
107 views

keeping keys on an auxiliary removable drive

It seems that servers are only as secure as the machine that holds the keys and that in turn means the desktop/screensaver password is the line of defence for not only the desktop itself but any ...
1
vote
0answers
793 views

Using Metasploit with 3G USB modem

I have a computer with Linux BackTrack 5 as host and Windows XP as guest on virtual box. I am using Host-Only-Adapter to create virtual LAN and to share USB modem internet as well so that both host ...
0
votes
1answer
2k views

What is the security impact of not using tls-remote with OpenVPN

Is it a security issue not using the tls-remote option in OpenVPN? That is not verifying the server's common name. Is a MITM attack possible? Could this be an issue, especially with services like ...
1
vote
1answer
152 views

Accounts attacked

I have run two commands below. I find some of the accounts attack as below. I do not have the account test,teste,oracle and admin in my home directory. As there system account. How to know which are ...
2
votes
3answers
1k views

How can I securely login remotely to my Linux box over the internet?

I'm pretty much a Linux beginner, but this question has been on my mind. What's the simplest, most secure way to connect to my computer at home from work or from the library, &c? I'm running Mint ...
2
votes
2answers
1k views

Moving a root directory to a separate partition

I'd like to create a new partition and move the contents of the /var directory to it for the security reason of having /var/www and other subdirectories "mounted" with nosuid, noexec, and nodev ...
1
vote
1answer
1k views

add members of wheel group, sudo access

On Fedora15, following this wiki, I added a user to wheel group, which is already in the sudoer config file. but still I get not-a-sudoer error prompt. Should I specifically name every member of a ...
43
votes
5answers
39k views

What is the point of sshd “UseDNS” option?

I know what it does, but i don't know why. What attack(s) does it prevent ? Is it relevant for all kind of authentication methods ? (hostbased, password, publickey, keyboard-interactive ...)
0
votes
4answers
866 views

securing SSH and disabling direct root

In these instructions below what appears on my terminal is different so not sure what I should change. After port 22 mine says #AddressFamily any and further down for protocol it has longer line ...
0
votes
0answers
85 views

Usage of stunnel for configuring secure services as a default?

Ok, I am aware nothing will beat manual security configuration through your standard daemon config files, but is it bad practice to configure stunnel for all services on say, a production ...
-2
votes
1answer
127 views

What software(s) should I install on new system(with Linux as a OS) to prevent it from getting hacked? [closed]

I am switching to new system with a OS using Linux.I will be using another system which has windows ultimate which is hacked.I am being cyber bullied. I have given a reference to this as a question on ...