Content related to computer security.

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4
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2answers
196 views

Shredding everything: files/folders and corresponding filenames

Using find, it is easy to shred a directory's contents recursively (as discussed in this question). However, sometimes the filenames on their own carry sensitive information already. Is there a way to ...
4
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3answers
240 views

Linux executable sandboxing?

I'm running a service that allows users to submit code which is compiled and executed on the server. At the moment I'm using Moe and while it works fine for C and C++ code, I've been having some ...
4
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3answers
224 views

Randomise or shred memory of an application

Is it possible to randomise or shred memory of a particular application just after its life ends, or better, whenever it deallocates some memory? A command-line utility like this would be perfect: ...
4
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2answers
69 views

What are the methods to protect home folder files from other applications runing as the same user?

I would like to enforce the security access of some files in my Home folder. My concern is about processes running with the same privileges as me having access to those files. I've been wondering ...
4
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3answers
129 views

restrict student account permissions, give faculty access

I have set up two user groups, students and faculty on Ubuntu 12.04 and created a number of students and faculty accounts. The problem is a student can currently see & read all of the files of a ...
4
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1answer
59 views

Is strace a suitable tool for finding out where a program wrote to the filesystem?

I'd like to determine where a certain app (as an example, surf) writes to the filesystem in order to make sure it leaves no traces. Without a dedicated sandboxing system this probably isn't easy, but ...
4
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2answers
391 views

How to identify a process which has no pid?

I have a process which listen to 2 ports : 45136/tcp and 37208/udp (actually I assume it is the same process). But netstat doesn't return any pid : netstat -antlp | grep 45136 tcp 0 0 ...
4
votes
1answer
51 views

TCP wrapper “except” option

I configured the /etc/hosts.allow at the machine 192.168.122.50 with the following option. sshd : ALL EXCEPT 192.168.122.1 and tried ssh root@192.168.122.50 from the machine 192.168.122.1 and I was ...
4
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2answers
2k views

How to find out out WHEN an user account was locked

With passwd -S user_name one can find out, if an account is locked, but is there a way to find out when it was locked and who it locked? Further links: http://serverfault.com/a/485760/78439 Disable ...
4
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2answers
786 views

Arch: Is “SigLevel = Never” the only convenient way?

The only way I can install majority of packages without rejection from signature database is to put SigLevel = Never in pacman.conf. Its not supposed to be the right way, but I don't seem to be able ...
4
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1answer
1k views

Disable random memory address generation in my programs

I'm reading "The art of exploitation" and would like to try some experiments, including reading from and writing to various memory address. I've created some simple programs and trying to overwrite ...
4
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2answers
1k views

BCRYPT - Why doesn't the Linux Distributions use it by default?

Does OpenBSD use bcrypt by default? Why doesn't every modern Linux Distribution use BCRYPT? http://codahale.com/how-to-safely-store-a-password/ https://secure.wikimedia.org/wikipedia/en/wiki/Bcrypt ...
4
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1answer
106 views

Is there any point in using `sudo` when you are the sole user of your machine?

I'd like to know if there is any reason why I should use sudo instead of su, taking into account that I am the owner and sole user of my machine (and hence have root access whenever I want). Also, in ...
4
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2answers
100 views

Is there something like one-time sudo?

Is there a way to have a one-time sudo account? My use-case is the following. I have an Ubuntu station with no remote ssh allowed to that machine. The machine generally serves as a public-use ...
4
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2answers
151 views

Understanding getlogin()

I think the previous iteration of this question was a little bit like a carpet bomb of questions, so that may have turned people off to it (to the point of almost being flagged for removal) so I'll ...
4
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2answers
1k views

Why is mount.cifs not installed suid by default?

I am using Gentoo, and on my machine at least mount.cifs is not installed suid root by default. In particular, this means that I can't use the user mount option with CIFS shares. I noticed that ...
4
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6answers
413 views

Any program like `sudo` to gain root by having two users enter a password?

I run a server which is used by a group of individuals for e-mail, mailing lists, personal web homes etc. I thought about ways to provide root access for other members to allow them handling problems ...
4
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1answer
781 views

Linux - why is kernel.shmall so low by default?

I run DB2 on Linux where I have to allocate the vast majority of memory on the machine to shared memory segments. This page is typical of the info that I've found about shmall/shmmax: ...
4
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1answer
47 views

What is not accessible from userspace?

I read somewhere (3.1.3) that there's a high ring (supervisor mode) and a low ring (user mode) and that some "things" can be run only from the highest ring. What do they mean by "things"? I'd guess ...
4
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1answer
417 views

What are EXT4 Security Labels?

During Gentoo installation of Gnome keyring, I am told to switch on EXT4 Security Labels, which is described in the kernel documentation by: Security labels support alternative access control ...
4
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1answer
835 views

How to configure permissions to allow apache to securely have access to a file in a shared environment?

This is a follow up question from my previous, but I felt it might be more Linux based. http://serverfault.com/questions/414207/how-to-set-linux-permissions-to-allow-apache-to-have-access-to-a-file ...
4
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2answers
498 views

How to set secure permissions for multiple users and multiple websites?

On a Gentoo 3.2.12 server with apache2+php, there are several websites running: /www /website1 /website2 ...etc The apache user should have read-only access to all the websites. There ...
4
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1answer
2k views

Linux: LUKS and multiple hard drives

I have a Debian Linux system (amd64) installed on a RAID-1 system encrypted device (LVM on LUKS) and will have a RAID-6 of >=4 disks where I'll put my data (LUKS and maybe LVM). I think the basic ...
4
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1answer
131 views

Mount and automount and security problems

Are there any security problems related with (auto)mounting device?
4
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1answer
174 views

How do I know which files will be included in a linux kernel before I build it?

I am working on a project that includes building an old kernel version of linux. This is fine, but I still need to patch the kernel of all previously found security vulnerabilities based on CVEs. I ...
4
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1answer
1k views

I don't want other users see my processes in ps aux. I have root. It's Debian. How to use grsec?

I installed 'linux-patch-grsecurity2' and it has some sort of interface. ~$ sudo gradm2 gradm 2.1.14 grsecurity administration program Usage: gradm [option] ... Examples: gradm -P ...
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1answer
123 views

How can I run keychain in a way that only has the first shell prompt for keys on startup?

I open multiple shell tabs when I start KDE, and I've just added keychain to my ~/.shellrc the problem is that all the tabs prompt for key passwords when I login. This is quite annoying to do this. Is ...
4
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1answer
80 views

Where are passwords stored and how are they encrypted in OS X?

I know that on a Linux system passwords are stored in /etc/shadow and are salted and encrypted using a one way hashing algorithm like MD5, SHA-256 or SHA-512. It looks like there is no /etc/shadow ...
4
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3answers
823 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 ...
4
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1answer
240 views

Confused about PAM configuration stanza and the roles of the control-flag parameters

I just begun studying for the RHCE. While on the topic of PAM configuration, I was a little perplexed with this stanza from /etc/pam.d/system-auth: auth required pam_env.so auth ...
4
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2answers
3k views

Can I create a local only guest account?

Is it possible to create a "guest" account in Linux? by "guest" account I mean an account that does not require a password to log in graphically. I want this account for when people come over and are ...
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1answer
20 views

Require private key for sudo

For added security, I would like to require a private key to use sudo on my Ubuntu Server box. I've added private key authentication for sudo as described at ...
4
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1answer
117 views

Myth or reality: SELinux can confine the root user?

I read or heard somewhere (maybe in LinuxCBT's SELinux course; but I'm not sure) that there are online Linux servers, for which the password of the root user is also given. The Linux server is ...
4
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1answer
87 views

Tomoyo Linux: Have a private folder, that can't be read by default

Is it possible to specify folders, eg: /home/$user/private that can not be listed, read or written to by any application in the default profile 0, but only with programs where I specify this as ...
4
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1answer
150 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
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2answers
259 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 ...
3
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3answers
260 views

Securely feeding a program with a password

After understanding the problem with using a password in the command line, I need to find a way of feeding a program with a password without it being a problem (without the password being recorded ...
3
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4answers
207 views

Internet SSH Server Security Considerations

What steps should I take to reasonably secure my linux desktop before opening sshd to the Internet so I can connect from anywhere?
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3answers
281 views

True HTTPS? How?

/Using Google Chrome/ if i visit: https://secure.wikimedia.org/wikipedia/en/wiki/File:Nokota_Horses_cropped.jpg then the: ...
3
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5answers
357 views

Protect folder from sudoers

Is there an ability to not allow sudoers view your folder (only you and root can access folder)?
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3answers
274 views

Setting execution right to whole directory - is it good or bad idea?

I have a zip file containing lot of files and directories for a certain application which should be running on Linux. Some files needs to be set as executable, but the zip file format afaik does not ...
3
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2answers
1k 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
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3answers
546 views

Is encrypting your web browsing via SSH to localhost useful?

For example, if I did an ssh -X to localhost and invoked Firefox, would that be enough to be considered safe browsing, like if done on some public wifi?
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4answers
2k views

File permission execute only

How can I set file to be executable only to other users but not readable/writable, the reason for this I'm executing something with my username but I don't want to give out the password. I tried : ...
3
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2answers
396 views

Is it possible for a CentOS system on EC2 to not have a bootloader?

I'm attempting to look for grub: [root /]# find / -iname "*grub*" /sbin/grubby /usr/share/man/man8/grubby.8.gz /usr/share/vim/vim70/syntax/grub.vim /usr/share/vim/vim70/ftplugin/grub.vim ...
3
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3answers
2k views

How secure is Ubuntu in Virtualbox on Windows host?

I have the most recent version of Ubuntu in Virtualbox on Windows 7 host. How secure will that be? I mean if I get malware on windows how will that affect the Ubuntu system I am working on?
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2answers
112 views

SSH when to use public key and password?

I think I understand the difference between Public Key authentication and Password. But how do I decide which one to use and which one is most secure in what situation? Can anybody give me some real ...
3
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3answers
315 views

Logging when limit Exceeds

Is there a log file that logs information when the values set in /etc/security/limits.conf are exceeded? If not is there a way to make it log when the values are exceeded?
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2answers
51 views

Process in user mode switch to kernel mode. Then the process will have root privileges?

According to http://www.linfo.org/kernel_mode.html in paragraph 7: When a user process runs a portion of the kernel code via a system call, the process temporarily becomes a kernel process and is ...
3
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1answer
82 views

Has my machine been compromised?

I have a bunch of lines in my machine if I use "ps aux". Here are the lines: samp 8413 0.0 0.0 968 564 ? S 12:28 0:00 ./ssh 150 samp 8419 0.0 0.0 956 380 ? ...