Home page logo
/

basics logo Security Basics mailing list archives

Re: Windows Messenger Pop-up spam
From: "Kevin Davis" <kevin.davis () mindless com>
Date: Tue, 7 Dec 2004 23:14:13 -0500

Disabling unneeded services is not an adequate protection from
malware.

It is an adequate protection from malware that tries to attack services.


Which is a subset of all malware. Probably a small subset. The goal is to protect from all malware.

There are tons of malware - in fact probably the majority that set up
their own "server" once it infects the target system.

If malware is already running on the system, the box is 0wned and
schould be rebuilt.

Of course some type of cleaning is required if malware gets on the box. Making a blanket statement that the box needs to be totally rebuilt at the slightest infection of spyware is extreme - at least for the home user. The point of the discussion was what is effective in repelling malware attacks and vulnerable conditions. You suggest that turning off all services and keeping your system patched is all that is needed. That's really quite ridiculous considering the various types of attack vectors that are being used - malware can get on your system in the form of BHO in your browser. Malware can get on your system by opening email. Malware can get on your system using IM, IRC, or unknowlingly downloading some cool program and it being a trojan. You can patch and turn off all the services you want and this won't keep the malware away - for the typical user.

And doing what you suggest will most likely set up the condition that when such malware gets on the box, the user will literally have almost no chance of finding out. At least with a firewall and AV software, there's a decent chance that it will be discovered.


That's where personal firewalls help.

No.

Yes.


A new, unknown process is trying to get out to the net - the firewall
will catch this and alert the user.

The firewall may possibly catch this and alert the user. Or the malware
may simply sneak around the firewall. Or disable it. You can't rely on
PFWs to control outbound traffic.

You never rely on anything 100%. It is possible that the malware will do as you say. But with your advice, it won't have to sneak around anything and will have a low probability of being discovered.

2. Get your systems behind a firewall (a personal firewall if a home
user).

Firewall on a router: very well. Personal Firewall: most likely not.
Yes, there are some exceptions, but their number is few.

3.  Get your system behind a router.

Local networks of any kind: of course. A single home computer: maybe,
but not a must.

4.  Harden system by turning off uneeded services.

That would be my second step. No services -> nothing to exploit. I would
consider using a Personal Firewall *only* if for some reason a service
can't be disabled or bound to a specific interface.

Again, you can't always turn off all services. Probably not even most of the time.


5.  Employ the use of virus and spyware scanners\blockers

Virus scanners may be useful.

Why would you think so? You seem to be claiming that using your method would grant you immunity from such things.

However, one should be aware of their
limitations, since each virus scanner is just as good or bad as its
virus definitions.

That goes without saying.

As for spyware scanners/blockers: I usually prefer to
not install spyware in the first place. Avoiding IE/OE helps. Much.

People also generally prefer not to install viruses. It would be nice if there was always a dialog popping up asking you if you wanted to install this virus or malware. You have to be realistic. You need to think in terms of users who aren't as savvy as you. You are putting absolutley no outbound checks in place. Of course avoiding IE and such helps, but that's a personal choice. In general practice, until the alternatives to OE\IE become the dominant players, people are going to use IE and OE. You can attempt to get people to use other things but don't count on it. Even if they do, having no outbound checks is really quite weak security. Even if there's only a 50% chance that something gets caught, it's worth it.

The small, inexpensive SOHO routers only block inbound traffic. If a
user gets some malware on their system, this helps them not.

Neither does a PFW. Once malware is running on your system, you're
toast. Period. Even Microsoft finally did understand that [1].

What is better - having an owned box and knowing it or having an owned box and having no clue?

And no, you're not toast if *any* malware is running on your box. In some (maybe many) cases, that may be true, but if I get a trivial spyware program installed, that does not require me to trash the box. In a corporate setting where there are canned images and plentiful network data storage to mitigate potential loss, that may be the most expedient solutions. Not necessarily the case at home.


If there's no LAN but just a single host with Internet connection,
then why does the box need to provide any services at all? IMnsHO.

You can't make a blanket statement like this for all cases.  In some
cases this would be true, in others not.

Lets take the Messenger service, for instance.  Some people should
*not* turn off the Messenger service.  Why?  Maybe they are running
one of the several virus scanning products that use the Messenger
service to alert the user of a virus problem.

Any AV software that uses the messenger service for notifying the
(local) user should be trashed *immediately*, because of major
incompetence of the vendor.

I agree but that approach doesn't always leave one with many choices. That's just one example. There are tons of software packages that install their own services - many of which are network related services. For instance, most AV software installs an automatic updating service. Sure you can turn it off, but the typical user will never remember to update their AV signatures. Which is worse - having that service running or having it turned off and AV software with 2 year old signatures?

I still fail to see *any* good reason why a single computer (no LAN)
should *not* have all services disabled.


Do an experiment. Take a box and install Windows XP on it and disable ALL of the services. Use the box for a few months as your primary box for doing everything including getting on the net.

  By Date           By Thread  

Current thread:
[ Nmap | Sec Tools | Mailing Lists | Site News | About/Contact | Advertising | Privacy ]