Security :: Understanding TCPdump And SSH Security
Jul 10, 2010
I have ssh open to one of my servers on a non-standard port. I have never seen anything to make me believe someone has cracked or even has tried to crack into the machine in the past. However, I was troubleshooting another issues I had and notice entries like this in my tcpdump output:
13:09:22.341390 IP 192.168.1.2.51413 > 190-82-164-231.adsl.tie.cl.10399: UDP, length 67
13:09:22.341427 IP 192.168.1.2.51413 > 95.58.5.15.22439: UDP, length 67
13:09:22.341464 IP 192.168.1.2.51413 > ool-4350a8e7.dyn.optonline.net.56836: UDP, length 67
13:09:22.341499 IP 192.168.1.2.51413 > 80.237.121.2.63878: UDP, length 67
13:09:22.396750 IP ool-4350a8e7.dyn.optonline.net.56836 > 192.168.1.2.51413: UDP, length 58
13:09:22.698354 IP 95.58.5.15.22439 > 192.168.1.2.51413: UDP, length 58
Obviously some of these are IP addresses of people on ISPs. Are these people just scanning ports? I do not see any invalid users in my secure log so I am not too concerned right now. But I am getting a ton of these (above entries) in my tcpdumps, so it is a little scary to think that there is this many people trying to scan my ports and possible attacking me. I am just trying to learn more about security and tcp packets.
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Apr 10, 2010
I've installed ClamTK on my Kubuntu 9.10 installation, since it's connected to a Windows7 machine.When I ran a scan, it found 9 'viruses', but they are all within my home directory > Opera/mail/store and are either status Phishing.Heuristics.Email.SpoofedDomain OR HTML.Phishing.Bank-593.I recently synced my Hotmail into Opera, so I checked the corresponding dates in my Hotmail account and deleted the emails which I thought were related, however, after clearing down my Opera history, etc., re-booting my PC and re-scanning, the results are the same.How do I clear down these files?
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Jul 20, 2010
On Windows, you can go to a file's permissions and it's clearly stated who can do what. You can choose between individual users or groups such as 'everyone' or certain types of users such as 'domain users'. You could create a clear cut list of every single user/group on the system and what their permissions for a file are and have it neatly displayed in a list.On Unix, we have octal permissions and sticky bits. I understand the whole concept of rwxrwxrwx (777). The first three are what the file owner can do, the second is what the main group the user belongs to can do, and the third is what other users can do.
But, when you view a file's permissions you are only getting the permissions as they apply to the user that owns the file. For example, as I understand it, if I viewed a file that only the root user had rwx permissions on and everyone else could only read. The permissions would show up as rwxr--r-- (744). But, those same permissions would show up to any user as 744 as well. Since the last 3 characters are what applies to "other users" (pretty vague). How would someone know what users in particular those permissions apply to? There could be one "other user" that can rwx that file and another "other user" that can't.Also, why just stop with the main group? What about other groups? A the user Foo's main group he belongs to might be Foo. But he could also belong to the groups Boo and Zoo, which belong to other users and would give him full rwx permissions over Boo and Zoo's files just as if he were Boo or Zoo.
Then you have the whole sticky bit thing that makes it so that files can be owned by the same person and at the same time be made use of (to varying degrees) by other users. To chmod the UID you'd chmod 2777 or for GID 4777 (just an an example). I did this for a file and it allowed a standard user account who was previously unable to run the command to be able to run it. But, how can that work when I didn't anywhere specify what particular user (or groups of users) that sticky bit applies to?
I'm confused about this whole thing to the point that I'm not even sure exactly what questions I should be asking or even if my examples are even 100% correct. I just sort of ranted about some specific things that floated to the top of my head. Permissions are easy to understand when your running a Unix-like system on a single user desktop. Because the only users/groups you have are root, the single user, and various system users/groups that you don't really need to worry about. So a file with rwxr--r-- means that only the Root user (not even members of his group) can edit the file and you can't unless you use sudo. Because the "other user" in the last 3 characters always just means you. But, things seem to get a whole lot more complicated when you start adding in multiple users. Can someone explain this or link to a "for dummies" article that can explain all of this to me in a way that someone who's used to Windows style permissions can make a connection between the two OS families and their way of handling these things?
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Apr 1, 2010
I was wondering how one could set up tcpdump to run in the background, dumping all output to a file until I terminate the process.Here is the dilema... I SSH into the box that will be listening (using tcpdump)...
ssh> sudo tcpdump -i eth0 > dump_file
yadda yadda...
then if I exit my ssh session, tcpdump closes.
If I do a...
ssh> sudo tcpdump -i eth0 > dump_file &
[1] 12938
yadda yadda.
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Feb 23, 2010
I'm not an iptables expert. Anybody know how to create a rule/chain that will log info similar to what tcpdump -s0 would do?
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Aug 13, 2011
I want to capture all packets from site "www.examplesite.com" so I checked its ip address in an ip address look up and it was 123.456.abc.def.So I set my filter to "dst host 23.456.abc.def"However I then realised that multiple ip address point to ww.examplesite.com, for example say the following ips also go to987.654.321.000111.222.333.444So is there a filter that will automatically capture all traffic going to www.examplesite.com or do I have to go and manually find all it's ip addresses and pass them all to the filter?
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May 22, 2011
love security/pentest tools. This script adds ALL the tools from the Security Spin, plus Metasploit. Feel free to modify it if need be.
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Jan 19, 2010
ubuntu 9.10 login panel is worse with respect to ubuntu 8 since now all the users with names are shown without a way to hide them!Why don't keep the old way at least as an option?
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Oct 15, 2010
To avoid having to input a password for the keyring each time I connect to the net via wireless, I enabled the 'Available to all users' option in Network Manager. Now, my question is this. Are the 'users' it refers to just those created on this machine? Would a drive-by be able to use my network without entering the password?
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Jan 17, 2011
1. I understand you can protect your files or directories in your website by setting file/directory permissions. The meaning of r w x is clear to me, but I'm not sure how to proceed... Starting with the index.html file, if I wanted to make it so that anyone in the world can read it but can't modify it, do I set its permissions to rwxr-xr-x? If I set it to rwxr--r--, would that mean the file couldn't be served? I mean, what does the x setting do on a .html file, how can a .html file be executable?
2. If file permissions work on the lines of owner-group-others, in the context of a website, who is 'group'? As far as I can tell, there's only the owner, which is me, and others, which is the world accessing the site. Am I correct in thinking that by default, say when creating a website on a shared hosting server, there is no group unless I specifically set one up?
3. My ISP allows the DynDNS.org service, meaning that I could serve a website from my home. It's too early to go that route just yet, but for future reference, I would like to ask about the server software called Hiawatha. It is said to be secure, but having read some evaluations of it, it doesn't seem to offer anything that couldn't be accomplished with Apache or Cherokee, it's just that its security settings are simpler and easier to configure. Am I right about this? Or does Hiawatha truly offer something that the other major server packages don't?
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Apr 13, 2011
this is the allert i got:Code:Summary:Your system may be seriously compromised! /usr/sbin/NetworkManager tried to loada kernel module.Detailed Description:SELinux has prevented NetworkManager from loading a kernel module. All confinedprograms that need to load kernel modules should have already had policy writtenfor them. If a compromised application tries to modify the kernel this AVC willbe generated. This is a serious issue.Your system may very well be compromised.Allowing Access:Contact your security administrator and report this issue.Additional Information:
Source Context system_u:system_r:NetworkManager_t:s0
Target Context system_u:system_r:NetworkManager_t:s0
Target Objects None [ capability ]
[code]....
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Mar 3, 2011
i updated both browsers i have and lost my secure log-in pages (no padlocks showing ) concerning different Web mail accounts.Just before i did these updates i checked an unrelated thing on-line regarding my sound card of which i kept a copy of and got this message below :
!!ALSA/HDA dmesg
!!------------------
[ 12.762633] cfg80211: Calling CRDA for country: AM
[code]....
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Apr 7, 2009
I'm just curious as to what security measure's I should be taking to make my box a little less vulnerable? I'm still experimenting/playing with Linux, use the net, IM, download this and that and was wondering how secure fedora 10 was out of the box?
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Apr 8, 2009
During a recent install I made the leap to encryption,but /boot must remain unencrypted.Is there really any legitimate security risk to having an unencrypted /boot partition? I mean basically someone can just see what kernel you're running which they could see during boot anyways right? Oh I and keep all my financial documents in /boot/finances/ (haha ok not really, but I am serious about the first part).
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May 30, 2010
Is it possible to install security lab menu on a normal Fedora 13 installation? I don't want to use security spin.
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Feb 3, 2010
Is there a way to delete files on the commandline that uses the KDE-Wastebin?It appears that I never ever need the KDE4 Wastebin for files that I deleted through Konqueror or Dolphin. It is only when I delete files on the konsole with rm that I wish I could undelete them. It always happens like that, mostly by being in the wrong directory or using a wildcard when I should not have. (I don't have any erroneous deleted file right now, and I do have plenty of backups, but I just wonder whether there is something better than rm to use generally on the commandline.)
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Mar 29, 2010
Conky can be used to display a variety of information on the users desktop. I wanted to use Conky instead to display the current status of security as reported by:
SANS Internet Storm Center
IBM Internet Security Systems
Symantec Threatcon
McAfee Threat Center
I therefore created 4 small scripts which download the current status from these sites, and set the colour of those status's depending on the current value.The conky configuration allows for a semi-transparent background - though this is optional.Attached is an example image showing the 4 different colours.Also attached is an archive with the 4.sh files, .conkyrc and draw_bg.lua (from here http:[url].....
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May 29, 2010
I just installed Ubuntu on a desktop. Can anyone give me some guidance on installing basic security software? In particular, I'm looking for a firewall, antivirus, and anti-spyware/malware utilities.
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Aug 3, 2010
I already posted a topic similar to this concerning the Desktop OS version, but this deals with the Netbook because unlike the Desktop, the Netbook is less cooperative. Allow me to elaborate: Today (or rather yesterday since it's not after midnight where I am), I changed my password because I was hopelessly confounded about how to get my Wireless Network card up and running after it had been installed and I was allowing my dad to use it. This issue has since been resolved, however...
When I chose my password during the original installation, there was no mention of it being "too simple." This is where the Desktop OS and the Netbook OS differ. The desktop will let me change it in the terminal without any errors. The Netbook will not. When I've attempted to revert it back to the original, it will not let me do so in the User Profile or in the Terminal. The Passwords and Encryption Keys application also does not appear to help.
So now even after I've changed it to a different "complicated" password I am still prompted to insert two different passwords since I changed my user password but I am unable to change the password I input during the installation. A bit screwy methinks. This is extremely important. I'd like to know how to change the original installation password.
If I can't change the main password on my laptop then this is a serious potential security breach just waiting to happen (especially since it's on a laptop and I will be hauling it around with me) and I will most likely install a different OS if this isn't resolved --- It would be very unfortunate since I spent the whole day fixing it and I really enjoy the interface. Luckily I can live with this on my Desktop since I'm not going to be hauling it around with me everywhere when the school year starts.
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Nov 11, 2010
As it stands I have a small home network operating behind my modem/router. Some of the ports on this are forwarded to my PS3 for gaming but I was looking at forward some for my file server.
At the moment I've forwarded port xxx22 to port 22 on my server for SSH for instance. ANd similarly 21 for FTP (although it doesnt seem to want to connect for any more than a few seconds using that). What I was thinking of doing was placing a small website for a handful of ppl to use on the server too and port forward again - xxx80 to 80. It works just fine but I'm a little concerned on the security front.
As I've moved the port to something different from the outside world I'm presuming I will have already cut the potential for malicious folks to wander in but is there anything else I should be doing? At the moment there's no firewall operating on the server, usually as its hidden behind the modem/router. But if I open this thign up more permanently what should I be doing? I've read a few articles on it but I'm always left with the overwhelming thought of "Thats if theres no firewall in my router" as they just seem to do the same.
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Feb 28, 2011
When posting results from ifconfig, it shows the hardware address of etho, etc. Would you consider that to be a security risk ?
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May 8, 2011
I'm concerned about security of having a LAMP server on my laptop as having any server makes the system less secure. However, if I were to create a new partition and install a lamp server on that and only use it when offline, would the security of my main partition be affected at all?
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Jun 7, 2011
The default Firewall ufw is not enabled by default at the time of installation and it has to be enabled by the user.Isn't this a security risk or is the user whether ufw is enabled or not secured from external threats?I am not much knowledgeable about network security But I am trying to understand the Ubuntu mentality behind this default setting.
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Jul 22, 2011
I've recently been running a game server from my desktop, as well as a web page to accompany it.I use the ports 80/8123(HTTP)/5900(VNC)/50500(GAME)/5839(ADMINISTRATION).What's the best solution to protect my server from security threats? On a side note, I plan on adding a MySQL server later, but I want to keep it local only.
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Mar 19, 2010
I've got a samba share on a linux server, connecting to it with a windows 2k3 server via tools > map network drive. The goal is to be able to use windows to change the security of the samba share. The good news is it works! The bad news is it's not QUITE perfect:
The share is called /company. I started with the following to give everyone access to everything, set the owner of the share to administrator (my domain admin on the Windows domain), and set the group owner to domain users (group that everyone on the domain is part of):
Code:
chmod -R 777 /company
chown -R administrator /company
chgrp -R domain users /company
I then mapped the drive as a regular user, and of course, can access/modify/delete/rename/create anything I want. Then I picked a folder to lock down. Let's call it /company/myFolder. I did this on the Windows server by mapping the drive as administrator (the owner), right click > properties > security tab > advanced > highlight "domain users" and "everyone" and click edit > clear all (i.e. remove all access). Go back to Linux and
[Code]..
The only issue that remains is that I am able to rename/delete "myFolder" as a regular user. I thought this was coming from the "acl map full control = true" parameter in smb.conf, but I changed it to false and verified the change and it still happens. If I remove group and world write access to /company, I am no longer allowed to rename/delete myFolder, but then I can't create a new folder. If I add group write access back in I can create files but can also rename/delete folders within /company that have --- specified for group access. Any ideas what I need to tweak to make this right?
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Jul 19, 2010
Currently I'm looking into implementing mod_security on all our apache servers. The installation on CentOS 5.5 comes directly with the "Core Rule Set" by the mod_security devs (curiously Debian and Ubuntu do not carry these) They also offer the Enhanced Rule Set for mod_security in a commercial package [URL] The main point there in their info link is the first point
Quote:
Tracking Credit Card Usage as required by the Payment Card Industry Data Security Standard However acc. to this wiki article ( http://en.wikipedia.org/wiki/Payment...urity_Standard ) that specific requirement isn't stated anywhere, as well as my colleague who's working on the PCI-DSS compliance for our code/servers/etc. mentioned that he hasn't heard of this specific requirement either. So my question would be if anyone has any experience with their ERS package and if it's needed for the PCI-DSS compliance compared to the requirements given in bullet points @ wiki article.
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Jan 30, 2010
I have a CentOS 5 server in which I use Virtual Hosting and each domain has its own user/pass for login to upload files. The path is /var/www/vhosts/domain name]/httpdocs/What im attempting is setting up the creation of the [domain name] folder from an administration backend under PHP, which I am developing. What Im worried about is if I allow PHP to run command line commands such as mkdir, then what is stopping anyone from doing the same from their php files on my server??? What is the best way to properly setup my server to allow automated creation of the domain structure within my folder system
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Mar 17, 2010
I am surprised (from the searches I carried out on the net) that no one seems to have considered this danger so far as I can see...I'm a little concerned about the implications on security for algorithms that opaquely shift data blocks around on disks to even-out surface wear rates.In the good old days, if I wanted to wipe a file that documented my struggle to give up frosted strawberry donuts (for example) I knew where that file started on the disk and how long it was and could thus instruct the OS to wipe it with complete confidence.
Nowadays, however, with increasingly sophisticated use being made of W-L techniques and fancy, journaling file systems that separate meta-data from file content and whatnot and so forth, how can I still be sure that when I try to overwrite a personal and private file, that i AM actually doing precisely THAT, and not just nuking some virtual image of the thing which in reality remains preserved elsewhere on the disk?
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May 12, 2010
I have an environment with multiple projects that have a variety of government and commercial sponsors. We have been satisfied to this point with a netapp serving nfs/cifs and keeping a tight reign on nfs exports.Some of these projects have started asking us to provide access restricted sub-folders of the project space based on different groups that contain a user subset of the primary group.
We have a linux machine that serves as a version control front end to the netapp, mounting the project spaces via nfs. People are now mounting their project space via sshfs to this "front end" and sharing the root password of this sshfs client with everyone in their project, in turn creating a security hole to access the so called restricted sub-folders. I know all the obligatory responses referring to irresponsible user behavior but would like to see how others have addressed something like this where user behavior seems out of control.
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Oct 10, 2009
If I leave the computer running for a few minutes without doing anything on it, this screen appears demanding that I enter my password, otherwise I can't get back to Fedora. I understand the necessity for this security feature in a work environment, but I'm just a home user and this security screen is just a nagging problem I don't know how to get rid of.
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