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.

learn more… | top users | synonyms

6
votes
3answers
12k views

Check outgoing network traffic

In Ubuntu, how can I check what information is being sent through the network connection, what programs are doing it, and what sites is my computer connecting to? I am not paranoid about security, ...
4
votes
3answers
242 views

Can someone execute a malware by just inserting a flash disk?

I know that Linux is virus proof, but just to be sure...Suppose someone writes a script, trojan, etc... and put it on a flash disk or CD. then I insert that flash in my system without clicking on any ...
8
votes
2answers
1k views

ssh-agent: don't forward authentication for the whole keyring

I have two private ssh keys : one to access my personnal machines, one to access servers at my job. I add those two keys to my ssh-agent with ssh-add. Now, when I do ssh -A root@jobsrv I ...
3
votes
1answer
906 views

Best way to encrypt my system on an ssd

I consider to buy an ssd for my laptop (something like Samsung 830 or 840) to make the system more responsive. I want my system (at least my home partition) to be encrypted. However I know about ...
1
vote
3answers
3k views

Taking away a User's Read/Write/Execute Permission

So I have a user that is able to go in /etc and read files like httpd.conf. I would like to deny that user access to any critical locations such as /etc, /var and so on. What would be the best way ...
2
votes
5answers
4k views

How to securely automate running commands as root with “sudo su -”?

hint (on client side, how to encrypt files/pwd's): # encrypt pwd with ssh key: openssl rsa -in ~/.ssh/id_rsa -outform pem > ~/.ssh/TEMP-id_rsa.pem 2>/dev/null openssl rsa -in ~/.ssh/id_rsa -...
10
votes
2answers
11k views

What does the Chromium option `--no-sandbox` mean?

I'm running Chromium like so : chromium --no-sandbox I'm doing this because I'm running Debian Squeeze on an OpenVZ VM Container and it's the only way I can get it to work. Though I keep reading ...
5
votes
3answers
3k views

Restrict ssh login from LDAP to users who have a /home directory

I have an Apache server (RHEL 6) hosting multiple user web pages which currently is connected to my Active Directory environment to authenticate users. The server is used to automatically host content ...
5
votes
1answer
405 views

How does having /dev/fd make running shell scripts under sudo safe?

At the end of the man page for sudo, there's the following remark: Running shell scripts via sudo can expose the same kernel bugs that make setuid shell scripts unsafe on some operating systems ...
0
votes
1answer
39 views

How to identify which application is trying to access the unixbuild server?

The error message I am seeing is: Failed publickey for raj from 10.*.*.** port 34355 ssh2 Mar 18 05:22:34 unixbuild sshd[16956]: [ID 1000034 auth.info] Failed password for raj from 10.*.*.* port ...
2
votes
1answer
226 views

Configure SSH keys for production and DR server

Here is the case, we have successfully configured SSH keys (and hence password-less SFTP connection) between ProdServer-A to ProdServer-B. It works, or so I thought still yesterday. Yesterday ...
5
votes
1answer
817 views

Ubuntu: If anyone can get a root prompt without password, isn't that compromising the gnome keyring?

I've been looking for this for quite a while now but couldn't find a satisfying answer. My scenario: I'm using encfs to encrypt a few directories in my home folder. To make it easier to access I set ...
26
votes
1answer
762 views

What would be the best way to work around this glibc problem?

I administer a Gentoo Hardened box that uses file capabilities to eliminate most of the need for setuid-root binaries (e.g. /bin/ping has CAP_NET_RAW, etc). Infact, the only binary I have left is ...
2
votes
1answer
606 views

Securely reading and parsing a string from a parameter or file in bash

I've been writing a number of bash scripts lately which get variables from a parameter or from a file. Some of the scripts run as root (using sudo) This is on my notebook, so there aren't any other ...
2
votes
5answers
3k views

How do I disable copy permissions?

Can we set permissions, on a Linux box OR for a particular directory (Scientific Linux in my case) that, one can read files but cannot copy, move or delete them? Update: My Scenario is, We developed ...
3
votes
2answers
9k 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
185 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
183 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 java-1.6.0-openjdk-1.6.0.0-1.56.1.11.8....
3
votes
1answer
359 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
250 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
1k 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
248 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
255 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 ...
17
votes
1answer
29k 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: ...
23
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
77 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
799 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
577 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
149 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
839 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?
2
votes
3answers
2k 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 ...
9
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
3answers
7k 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
95 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
3k 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
76 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
443 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
528 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 ...
2
votes
0answers
133 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 me,...
6
votes
2answers
778 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
316 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 ...
19
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
128 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 ...
10
votes
1answer
4k 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
528 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
802 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
728 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 ...