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Linux Security

The Linux operating system, in all its flavors, has its own share of security flaws that allow intrusions, but there are various mechanisms by which these flaws can be removed, generally divided into two parts: authentication and access control. Authentication is responsible for ensuring that a user requesting access to the system is really the user with the account, while access control is responsible for controlling which resources each account has access to and what kind of access is permitted.

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Hi,
I'm comparing these two lines in the audit.rules files.

-a always,exit -F arch=b32 -S clock_settime -F a0=0 -k time-change

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-a always,exit -F arch=b32 -S clock_settime -k time-change

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Could you please tell me the what -F a0=0 stands for?
Thank you
Carlettus
0
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i install ssh in ubuntu. i start services and it's  runnig. idisabled firewall. i add keygen in authorized_keys.
ssh <ip_host> says  Permission denied (publickey).
0
BACKGROUND:
A ways back, I'd set up nameservers on my VPS (let's call them 'ns1.mydomain.com' and 'ns2.mydomain.com').  I host a couple of dozens websites on that VPS.

For all of my domains, on the domain registrar's site, I'd set the Nameservers for that domain to Custom Nameservers:  'ns1.mydomain.com' and 'ns2.mydomain.com'.

Recently, I had to ask my VPS provider to create a new server for me (let's call it 'newVPS'), leaving my previous VPS (let's call it 'oldVPS') active so I could migrate or re-create accounts and contents from the oldVPS to the newVPS.

Both the oldVPS and newVPS use WHM/CPanel admin interfaces.  
The oldVPS is setup as (cut and pasted from the WHM panel banner): 'CENTOS 6.9 i686 virtuozzo – oldvps  WHM 56.0 (build 52)'
The newVPS is setup as (cut and pasted from the WHM panel banner): 'CENTOS 7.4 virtuozzo [newvps]  v68.0.21'

My understanding (which is limited in these areas) is that the nameservers I setup on my VPS have to be associated with one of the domains I own/host on that VPS.

The nameservers which I had previously setup on oldVPS were associated with 'mydomain.com' one of the domains/accounts hosted on oldVPS.  

For simplicity, I'm thinking of creating new nameservers on newVPS and associate them with 'myotherdomain.com', another domain/account to be hosted on newVPS.

QUESTION:
How do I create my new nameservers on newVPS, say 'ns1.myotherdomain.com' and 'ns2.myotherdomain.com', presumably from newVPS's WHM (I'm …
0
hi,

we have about 3 users say user1, user2, user3 on the weblogic server. The application logs and server logs getting filled up every 3 weeks or so causing server to choke. How to write a script to clean automatically those application log and server log folder contents automatically say every week on friday midngiht at 11 PM

please advise
0
I am getting this error message, when I was trying to run rpmbuild --rebuild lin_tape-3.0.23-1.src.rpm on Red Hat Linux 7.4 (Kernel version: 3.10.0-693.1.1.el7.x86_64). Can some one let me know what is problem and what should be the proper procedure to fix it. Here is the output mentioned below,

#rpmbuild --rebuild lin_tape-3.0.23-1.src.rpm
Installing lin_tape-3.0.23-1.src.rpm
Executing(%prep): /bin/sh -e /var/tmp/rpm-tmp.sCvFVM
+ umask 022
+ cd /root/rpmbuild/BUILD
+ cd /root/rpmbuild/BUILD
+ rm -rf lin_tape-3.0.23
+ /usr/bin/gzip -dc /root/rpmbuild/SOURCES/lin_tape-3.0.23.tgz
+ /usr/bin/tar -xf -
+ STATUS=0
+ '[' 0 -ne 0 ']'
+ cd lin_tape-3.0.23
+ /usr/bin/chmod -Rf a+rX,u+w,g-w,o-w .
+ exit 0
Executing(%build): /bin/sh -e /var/tmp/rpm-tmp.KGligF
+ umask 022
+ cd /root/rpmbuild/BUILD
+ cd lin_tape-3.0.23
++ echo x86_64-redhat-linux-gnu
++ cut -f 1 -d -
+ p=x86_64
+ '[' x86_64 == i386 ']'
+ '[' x86_64 == i586 ']'
+ '[' x86_64 == i686 ']'
+ '[' x86_64 == ppc64 ']'
+ '[' x86_64 == powerpc ']'
+ '[' x86_64 == powerpc64 ']'
+ '[' x86_64 == s390 ']'
+ '[' x86_64 == s390x ']'
+ '[' x86_64 == ia64 ']'
+ '[' x86_64 == x86_64 ']'
+ proc=AMD
+ make KERNEL=3.10.0-693.1.1.el7.x86_64 PROC=x86_64 SFMP=0 driver
make: Nothing to be done for `driver'.
+ exit 0
Executing(%install): /bin/sh -e /var/tmp/rpm-tmp.hQeoFx
+ umask 022
+ cd /root/rpmbuild/BUILD
+ '[' /root/rpmbuild/BUILDROOT/lin_tape-3.0.23-1.x86_64 '!=' / ']'
+ rm -rf …
0
I'm trying to run x11vnc with the --passwdfile option. This option sends a challenge string to the VNC client. The client opens a dialog on the user's screen asking for a password. The client then sends the response string back to the VNC server. The VNC server calls the program referenced by the --passwdfile parameter with this string in the following format:

A two-byte length (in this case 16), followed by the challenge string (16 bytes), followed by the response string (16 bytes). What I get back, in hex is:
 0: 0A 6E 65 78 74 0A 31 36 0A 23 36 F4 E1 03 EE 30    .next.16.#6....0
10: 16 85 FC E9 4C F1 F5 16 5C 2C D5 5C 93 C2 21 29    ....L...\,.\..!)
20: 3A DF C2 A2 7C E9 1F 1A D7                         :...|....

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The <newline>next<newline> can be ignored as this is debug stuff from my script. The strings are:
Challenge:
23 36 F4 E1 03 EE 30 16 85 FC E9 4C F1 F5 16 5C

Response:
2C D5 5C 93 C2 21 29 3A DF C2 A2 7C E9 1F 1A D7

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The manpage defines the response string as, "client's response (i.e. the challenge string encrypted via DES with the user password in the standard situation)." I have no further information or documentation. I assume one must use the challenge string to decode the response string and get the user-entered password, but I've no idea how to do that.
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hi

How to Make The Text Cursor Automatically when i'm on console text ?
I use directly on boot the tty console and desactivate graphical mode.

Thanks for your reply,

someone talk me about : /etc/inittab, or /etc/fstab
But i don't think it's good idea to modify 2 by 5
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I’m having trouble setting up LUKS on a Red Hat Test Server. I decided not to have a DEV prompt for a passphrase at boot but to use manual decryption instead. This is supposed to require execution of the cryptsetup commands and mounting. I attempt to set it up on a blank second disk I recently installed. Here’s the session…

**************************

sudo cryptsetup luksOpen /dev/sdb crypt-sdb
# enter /dev/sdb password

sudo cryptsetup luksClose /dev/sdb crypt-sdb

**************************



This then caused RHEL to freeze and force a cold reboot. I then used yum to run updates. I try again…



**************************

sudo cryptsetup luksOpen /dev/sdb crypt-sdb
# enter /dev/sdb password
#[<username>@localhost dev]$ sudo cryptsetup luksClose /dev/sdb crypt-sdb
Device sdb not found

# [<username>@localhost dev]$ sudo mount /dev/sdb
mount: can't find /dev/sdb in /etc/fstab

**************************



So I attempt to enter /dev/sdb in /etc/fstab but unsuccessful since it’s read-only. I try this.



**************************

[<username>@localhost etc]$ sudo cryptsetup luksFormat /dev/sdb
[sudo] password for <username>:

WARNING!
========
This will overwrite data on /dev/sdb irrevocably.

Are you sure? (Type uppercase yes): YES
Enter passphrase:
Verify passphrase:
Cannot format device /dev/sdb which is still in use.
[<username>@localhost etc]$ sudo umount /dev/sdb
umount: /dev/sdb: not mounted
[<username>@localhost …
0
I am using rubinus 3.86 and CentOS7(x86_64).
The installation directory is / var / home / ap / rubinius.

I attempted to install nio4r using the gem command and it failed.
The log at that time is as follows.

It is described as "method_missing", but what does it mean?

cat /var/home/ap/rubinius/gems/extensions/x86_64-linux/2.3/nio4r-2.1.0/gem_make.out

current directory: /var/home/ap/rubinius/gems/gems/nio4r-2.1.0/ext/nio4r
/ var / home / ap / rubinius / bin / rbx -r ./siteconf20171112-15122-n0ryc2.rb extconf.rb --with-ldflags = - L / var / home / lib / gcc5 / lib64
checking for unistd.h ... yes
checking for sys / select.h ... yes
checking for poll.h ... yes
checking for sys / epoll.h ... yes
checking for sys / event.h ... no
checking for port.h ... no
checking for sys / resource.h ... yes
                  main # Rubinius :: Loader at core / loader.rb: 861
                script # Rubinius :: Loader at core / loader.rb: 679
           load_script. Rubinius :: Code Loader at core / code_loader.rb: 590
           load_script # Rubinius :: Code Loader at core / code_loader.rb: 505
            __script__ # Object at extconf.rb: 21
   << (method_missing) # Kernel (NilClass) at core / zed.rb: 1413

undefined method `<< 'on nil: NilClass. (NoMethodError)

An exception occurred running extconf.rb
*** extconf.rb failed ***
Could not create Makefile due to some reason, probably lack of necessary
libraries and / or headers. Check the mkmf.log file for …
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On SLES 12.2 I do the following as root user:

mkdir -p /some/directory/ramdisk
chown -R simpleuser:users /some
chmod 777 /some/directory
chmod 777 /some/directory/ramdisk

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Then I add this to /etc/fstab:
ramfs /some/directory/ramdisk ramfs defaults 0 0

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followed by
mount /some/directory/ramdisk

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What I expect is a ramfs mounted to /some/director/ramdisk, owned by simpleuser and users, with permissions set to 777.

Surprisingly, after rebooting the machine, the owner of /some/director/ramdisk is root:root, and the permissions have changed to something more restrictive. I deem that more of a feature  than a bug, but that behaviour is really annoying in the environment I use it in.

Currently I do an explicit change of ownership and permissions prior to starting the application that uses the ramdisk (in the respective script, with sudo), but I deem that not very elegant.

Any hint what causes the changes, and how to prevent them ?
0
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1. Centos server 6.9 in AD = OK

2. Only access feathers for users of group_USER_AD, applying control via /etc/security/access.conf = OK
3. Blocked root access directly to no server. /etc/ssh/sshd_config (PermitRootLogin no) = OK

 4. To use local account, you will need to use "su -" and do not log in without server with local account = OK

----------------

I have an application that runs with a local account. How can I release the user's access to use the winscp tool and write the application's non /home? Attempts without success

1.) Add the network user's AD group within the application's local group.

2.) There are many network users AD. I can not add one by one in the local group.

How do I solve it?
0
Can i able to connect SuSE linux to Redhat satellite and patch?
0
Hello ,

I have a problem with interfaces on a multihomed topology. My interfaces can not ping each other and can not ping theirselves too
sysctl as given below.

But it is able to ping the interface ip when i directly write ping 37.123.98.142 , if the both interface are not able to ping this interface's ip how does it ping it or from where ?

I have to let them have access each other how shoud i do it ?

Note: loopback interface activated
Note2: em interfaces are all down

[root@spd network-scripts]# sysctl -p
net.ipv4.ip_forward = 1
net.ipv4.conf.p1p1.rp_filter = 2
net.ipv4.conf.p1p2.rp_filter = 2
net.ipv4.conf.all.rp_filter = 2
net.ipv4.conf.default.rp_filter = 2
net.ipv4.conf.lo.rp_filter = 2
net.ipv4.conf.p1p1.accept_local = 1
net.ipv4.conf.p1p2.accept_local = 1
net.ipv4.conf.all.accept_local = 1
net.ipv4.conf.default.accept_local = 1
net.ipv4.conf.lo.accept_local = 1
net.ipv4.conf.default.arp_filter = 0
net.ipv4.conf.all.arp_filter = 0
net.ipv4.conf.p1p2.arp_filter = 0
net.ipv4.conf.p1p1.arp_filter = 0
net.ipv4.conf.lo.arp_announce = 2
net.ipv4.conf.all.arp_announce = 2
net.ipv4.conf.default.arp_announce = 2
net.ipv4.conf.p1p1.arp_announce = 2
net.ipv4.conf.p1p2.arp_announce = 2

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PING 37.123.98.142 (37.123.98.142) from 37.123.98.142 p1p1: 56(84) bytes of data.

^C
--- 37.123.98.142 ping statistics ---
3 packets transmitted, 0 received, 100% packet loss, time 2055ms

[root@spd network-scripts]# ping -I p1p1 37.123.98.138
PING 37.123.98.138 (37.123.98.138) from 37.123.98.142 p1p1: 56(84) bytes of data.

^C
--- 37.123.98.138 ping statistics ---
4 packets transmitted, 0 received, 100% packet loss, time 3064ms

[root@spd network-scripts]# ping -I p1p2 37.123.98.138
PING 37.123.98.138 (37.123.98.138) from 37.123.98.138 p1p2: 56(84) bytes of data.

^C
--- 37.123.98.138 ping statistics ---
2 packets transmitted, 0 received, 100% packet loss, time 1038ms

[root@spd network-scripts]# ping -I p1p2 37.123.98.142
PING 37.123.98.142 (37.123.98.142) from 37.123.98.138 p1p2: 56(84) bytes of data.

^C
--- 37.123.98.142 ping statistics ---
3 packets transmitted, 0 received, 100% packet loss, time 2060ms

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[root@spd network-scripts]# ping 37.123.98.142
PING 37.123.98.142 (37.123.98.142) 56(84) bytes of data.
64 bytes from 37.123.98.142: icmp_seq=1 ttl=64 time=0.019 ms
64 bytes from 37.123.98.142: icmp_seq=2 ttl=64 time=0.022 ms
64 bytes from 37.123.98.142: icmp_seq=3 ttl=64 time=0.017 ms
64 bytes from 37.123.98.142: icmp_seq=4 ttl=64 time=0.015 ms

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0
Hello ,

Is there any possible way to drop bogus packets as seem below .

for this packets ; packet payload is smaller then the length of the packet

 Screen-Shot-2017-08-23-at-22.22.46.png
0
Hi Experts

I am trying install CentOS 6.8 minimal thru kick start on an Virtual Machine(VMware workstation) and assigning kickstart file thru http on another VM, kickstarts goes thru smoothly creates partitions and all but stuck on repo section unable to find repo following types of error, errors attached

Stuck with this error from few days, Please help

In /var/www/html location has ks.cfg file and all centos 6.8 minimal dvd content as it is

[root@srv1 html]# ls
CentOS_BuildTag  isolinux                  RPM-GPG-KEY-CentOS-6
EFI              ks.cfg                    RPM-GPG-KEY-CentOS-Debug-6
EULA             Packages                  RPM-GPG-KEY-CentOS-Security-6
GPL              RELEASE-NOTES-en-US.html  RPM-GPG-KEY-CentOS-Testing-6
images           repodata                  TRANS.TBL

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Section of kickstart file i am assign is shown below
# Kickstart file automatically generated by anaconda.

#version=DEVEL
install
url --url=http://10.0.0.11/
text
lang en_US.UTF-8
keyboard us
network --onboot yes --device eth0 --mtu=1496 --bootproto static --ip 10.91.48.17 --netmask 255.255.255.224 --gateway 10.91.48.1 --noipv6 --nameserver 8.8.8.8 --hostname nac17
network --onboot no --device eth1 --bootproto dhcp --noipv6 --hostname nac17
rootpw  --iscrypted 
# Reboot after installation
reboot --eject
firewall --disabled
authconfig --enableshadow --passalgo=sha512
selinux --enforcing
timezone --utc Asia/Kolkata
#bootloader 

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0
Hi,

I am working on a tenable nessus audit file for ibm aix.

What i am trying to achieve is 2 compliance check on the /etc/hosts.equiv file:

1. To find all UID less that 100 and UID not equals to the default system user ids (0,1,2,3,4,5)

2. To find all GID less that 100 and GID not equals to the default system group ids (0,1,2,3,4,5)

<custom_item>
type: CMD_EXEC
description: "UID less than 100 and not system default UID"
cmd: ""
expect: ""
</custom_item>

<custom_item>
type: CMD_EXEC
description: "GID less than 100 and not system default GID"
cmd: ""
expect: ""
</custom_item>

I am really new to working with tenable and also new to aix.

Really apperciate if anyone can help me out with what i should put for the cmd and expect statement on how to make the compliance check work.

Thanks really apperciate it!

Link: https://www.ibm.com/support/knowledgecenter/ssw_aix_71/com.ibm.aix.security/passwords_etc_passwd_file.htm
0
We need to have a standalone IPS solution put in.  We currently run two pfSense firewalls in an HA setup.  I was looking around on eBay and saw a Tipping Point 210E (two of them).  Are they still good with updates to definitions?  Any other less cost recommendations?
pfSense HA works a little odd too, so I'm not sure if this will even work.
Firewall 1 WAN IP x.x.x.1
Firewall 2 WAN IP x.x.x.2
Firewall Shared WAN IP x.x.x.3

Same setup with internal LAN IPs.  Each firewall has its own physical connection to the modem via ethernet for the WAN side and LAN side.
0
Hello Folks,
I have a few users to create for centos, and I would like to set them with restrictions such "system tools, create shortcuts, folders...similar to a kiosk " is there any way to do that or is there a special profile that needs to be created?

thanks for looking
0
I need to connect a Virtual Machine hosted somewhere running CentOS 6 to a client which is allowing connection through VPN only. However I have almost no knowledge about VPNs. The client has given me following info for connection:

VPN Remote Endpoint: <IP Address given by the client>
VPN Hardware: NGX R75.45 (SPLAT)

IKE (Phase 1)
==================
Authentication Method: Pre shared key (TBA)
DIffie-Hellman group: DH-2
Encryption Algorithm: AES-128
Hashing Algorithm: SHA-1
Renegotiate IKE: 14400 seconds

IPSEC (phase 2)
======================
Encryption Algorithm: AES-128
Hashing Algorithm: SHA-1
Renegotiate IKE: 3600 seconds
PFS Enabled: Yes

I am not sure where to put all these info in CentOS to make it to connect to the client's network.

I will be much thankful for any help.
0
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Dear All,

We have created a chrooted jail environment for our SFTP access. Using chrooted environment, we restrict users either to their home directory or to a specific directory. Now my question is if there's anyway we can an additional username to access the same home directory for other username? Or any other words, is there anyway I can assign different usernames to the same home-directory and have it chrooted jail?

Below is our current config if that helps:

group add sftponly


vi /etc/ssh/sshd_config

#Subsystem sftp /usr/libexec/openssh/sftp-server
Subsystem sftp internal-sftp
Match Group sftponly
ChrootDirectory %h
ForceCommand internal-sftp
X11Forwarding no
AllowTcpForwarding no

systemctl restart sshd.service

useradd USERNAME –g sftponly –s /bin/false
passwd  USERNAME


mkdir /home/USERNAME/SFTPWRITE
chown root /home/USERNAME
chmod 755 /home/USERNAME
chown USERNAME /home/USERNAME/SFTPWRITE
chmod 755 /home/USERNAME/SFTPWRITE

setsebool –P ssh_chroot_rw_homedirs on
0
On RH 6 systems running rsyslog 5.8.10 we noticed that if we setup a
client system to use TCP to log to a remote server:
*.*       @@192.168.1.2

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If the remote log server is not reachable for some reason no logging takes place, not even local logging to the local system log files.
When the log server is available and rsyslog is restarted  both local logging and remote logging work.   I would like to come up with a config that would ensure that local logging still occurs when  the TCP remote server is down?  I think I need to look at action queues, but was hoping someone could provide an example on how to get this to work.
0
I have nas disk mounted as nfs mount point i linux. how to create a dd image of this. the mount point is like that
s
tor01-nas.llg:/export/shared/ps_oem   nfs     2G  9.9K  2G    1% /oem1
0
Having a hard time trying to add to the domain a machine using Arch Linux, somehow I managed to sort of make the machine to join the domain but when it comes to the authentication part the computer won't recognize the credentials. Has anyone had luck doing this? if so can someone please help with the proper commands to make this work? Been dealing with this issue for a week now and I'm getting really frustrated. Bottom line if there's an easier way to make this machine to join the domain and authenticate properly that would be fantastic.

Many thanks in advance to anyone with the answer out there!
0
I have just installed my first IPA-Server (using CentOS) and it is already set as the LDAP server hosting the centralized credentials control from many users login on to many Ubuntu servers.

My problem is that I have tried to set a new group created in the IPA Server in order to assign SUDO permissions for the users login on to the Ubuntu servers using the LDAP accounts but it is still not working.

Does any expert has experience configuring IPA-SERVER.
0
Hi all...

Need to integrate with Ubuntu and other Linux systems. Basically, I would like to pass AD credentials on the network to a Linux system integration. I hope my question makes sense and looking forward to any ideas out there.

Thanks
0

Linux Security

The Linux operating system, in all its flavors, has its own share of security flaws that allow intrusions, but there are various mechanisms by which these flaws can be removed, generally divided into two parts: authentication and access control. Authentication is responsible for ensuring that a user requesting access to the system is really the user with the account, while access control is responsible for controlling which resources each account has access to and what kind of access is permitted.

Top Experts In
Linux Security
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