Hot answers tagged operating-systems
193
You are touching a sore point...
Historically, computers were mainframes where a lot of distinct users launched sessions and process on the same physical machine. Unix-like systems (e.g. Linux), but also VMS and its relatives (and this family includes all Windows of the NT line, hence 2000, XP, Vista, 7, 8...), have been structured in order to support the ...
105
In some places they have a saying: "opportunity makes the thief". All you're doing by screen-locking a computer is making the cost of hacking it just a little bit harder.
Security is an economic good, with a price and a value. The value of locking is somewhat larger than the price of locking it. Sort of like how in good neighborhoods, you don't need to ...
53
It's a risk management thing, really. An attacker with a short window of opportunity (e.g. whilst you're out getting coffee) must be prevented at minimum cost to you as a user, in such a way that makes it non-trivial to bypass under tight time constraints.
Hitting WinKey+L or clicking the lock button is next-to-zero cost for you as a user. Taking the time ...
26
I think the OS do his jobs and avoid processes to access other's allocated memory. But I think this is somehow doable.
Yes, it is possible to access the memory of another process. On Windows, this amounts to having SE_DEBUG_PRIVILEGE and using ReadProcessMemory() to extract the information you want.
You can do the same thing from a Windows Driver, ...
24
Locking your computer prevents surreptitious snooping or alteration. If you don't lock, it is easy for someone to poke around inside your session in such a way that you will not notice it when you return to your machine.
The security benefit is real because there is a class of attacker who wants access without leaving any trace whatsoever. For that class of ...
23
There is quite a lot of them:
Metasploitable: Currently there are 2 versions.
Kioptrix: Currently 4 challenges.
Hackademic: Apparently 2 VM, check 1 and 2.
pWnOS: Currently 2 challenges.
Standalone which you can install directly without VM, this is to hone your Webattack-Fu:
OWASP WebGoat
Damn Vulnerable Web Application
Mutillidae
23
There are a number of reasons why building their "own OS" is not a viable option.
1. Research Cost
To built a new OS, from ground up without the use of any existing code would require significant research. Even today, there are only four or five popularly used kernels like Unix , Linux kernel, BSD, XNU and Windows NT.
2. Security through obscurity
It's a ...
18
"What's the point of locking a computer besides keeping the average coworker from messing with your stuff?"
By protecting your self from average coworker you've protected your self from largest subset of people who'd want to find something personal about you or do you harm.
14
The underlying idea of the comic is that separation of user accounts has been designed for mainframes: big computers, shared by many users. In that model, the potential attackers are other users. Account separation is then about protecting users from other users; only the god-like admin account can access everything on the machine, and the administrator has ...
13
I work in the consumer electronics arena and security here is somewhat different than in the server environment. Here we have to assume that the product is in a hostile environment. So for subscriber management purposes keys are kept secure. The first line of defence is that the SoC has hidden registers that even the operating system can't actually access, ...
11
In most environments where it is necessary to lock your computer, what you are protecting isn't on your computer, but on networked computers which you have access to through your credentials. So a quick boot using a CD doesn't directly give the attacker anything useful, it is just a single step. While you are right that ultimately this isn't a barrier to a ...
10
Yes, it does store it unencrypted on the disk. It's a hidden file at C:\hiberfil.sys, which will always be created on any system that has hibernation enabled. The contents are compressed using the Xpress algorithm, the documentation of which is available as a Word document from Microsoft. Matthieu Suiche did a comprehensive analysis of it as a BlackHat ...
10
What language/platform are you using?
If it's .NET, check out the PasswordBox control and the SecureString class.
The SecureString class represents a way to store the password in memory without making it accessible to anyone - even hackers who sneak peeks at your application's memory.
The PasswordBox control is a textbox that incorporates the ...
9
GreenHills Software is a company that specializes on creating OSes for military embedded systems. Their INTEGRITY system uses a microkernel (less code with less bugs) that has been formally verified (even less bugs).
Such special-purpose domains, where only the most basic software components can be re-used, are probably the only area where it is manageable ...
9
Security is not only about the document located on your computer. Without a proper authentication to the company, someone having access to your machine should not have access to your emails (unless stored locally) and can't access network resources with your name.
When we say that having physical access is like losing this machine, it also implies that the ...
8
It takes time to boot to a live CD
Modifying the hardware will attract attention whilst simply using someone else's PC won't
More people will attempt to use an unlocked PC then a locked one in the same way you're more likely to have your bike stolen without a bike lock than with an unlocked bike lock on it.
8
In addition to all the other answers, think about skill. If I come across an unattended, unlocked laptop, it takes no particular skill to send an email from that computer to the Company President; that email can range from prank to criminal activity. The other attacks you describe require a bit more skill.
Reinforcing what others have said, security is ...
7
Answer first, then why: A virtual machine can be more secure.
From a practical standpoint, there exists code and malware that can infect both boot partitions, BIOS, and also hardware devices. So, a VM has slightly more advantages in a reduced attack surface from a generic point of view - potential VM hopping code is the largest one specific to the VM. ...
7
Like when doing car maintenance, when you know which constructor, you will take the right maintenance manual (Don't try to repair a Ford Granada with the manual of a Honda civic).
When trying to break a particular system, you will browse for known exploit that could help you for this particular system.
Every net servers (From Sendmail to Apache, with ...
7
So if I was you I would start relatively simply with some VMs and a host machine.
Personally I use VMWare workstation but other virtualization products are possibilities.
If you've got a decent enough machine (e.g. 8GB RAM, Quad-Core Sandy/Ivy bridge, fast disks), I'd recommend keeping the Host OS clear of lab tools or target Apps, as re-building VMs is an ...
6
TCP and UDP ports 111 are the well-known ports for ONC RPC portmapper. Portmapper is analagous to DNS, in that an RPC server registers with the portmapper process on the machine they both run on. An RPC server gives the portmapper the port(s) on which the RPC server listens for requests, and the (hopefully unique) number that identifies the interface or ...
5
You can't ever make something completely secure and still make it accessible. Therefore, you can't ever prevent anyone from gaining access to your computer system. All you can do is make it harder for them to gain access. And in the case of locking your screen, a simple two-second stroke of the fingers can bring great inconvenience to someone wanting ...
5
In addition to all the software attacks exploiting OS vulnerabilities if an attacker has physical access to your machine they can potentially read your keys directly out of your memory.
How can the impact of cold boot attacks be minimized?
5
if the hard drive stolen and cross OS are two different condition!
If stolen, mounted in another host, all permissions are compromised, everybody could be root in his host and mount hard-drive (maybe externaly by USB - Sata changer) with all needed rights. For this condition, (strong) encryption are the only way.
About cross OS, if drive stay mounted in a ...
4
Portmapper can allow an attacker to quickly determine if you run a vulnerable service. However, blocking portmapper isn't really sufficient since they can just call procedure 0 on open ports to find the services.
If you don't need external access to your onc rpc services, don't permit it.
4
Another good one is http://exploit-exercises.com/
"exploit-exercises.com provides a variety of virtual machines, documentation and challenges that can be used to learn about a variety of computer security issues such as privilege escalation, vulnerability analysis, exploit development, debugging, reverse engineering, and general cyber security issues. "
4
You give them Local admin rights to their workstation and anything else they want. The development environment is always isolated from the main network. It is IT's job to make sure you provide them with what ever setup they need while making sure nothing in the dev environment can harm the main network. Plan ahead and work with management to buy the ...
4
Personally this sounds like it's bordering on paranoia for people who aren't doing research on malware.
If you're running 2 different OS's, you'd need malware that knows how to read the two difference filesystems.
If it's running in a VM, you would need the malware to be specifically targeting the hypervisor so it can break out of the sandbox.
You're ...
4
To answer your specific questions
Never use the root account, always use a normal user account
An up to date, patched one
Generally considered a good idea, but good online banking applications should enforce no memorisation of passwords etc
This doesn't mean anything in this context - what do you mean by port and closed here?
Any plugin could increase the ...
4
You do not call functions inside the kernel. The kernel resides in another privilege level; its memory pages are not accessible from normal code. To jump into kernel code, application code performs a system call which entails using a specific doorway which handles the temporary privilege escalation. On a 32-bit x86 system running Linux, this is done with int ...
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