True Insight

As you may know, our company provides 24×7 Network Security Monitoring services to many customers.  Our clients vary widely in size, industry, and information security maturity.   Even so, we see many similar successes, failures, and trends in security monitoring alerts between these customers.  Spyware infections tendsto be a significant number of the incident reports we generate.  Today, I would like to write about the reason spyware alerts are a threat to your organization, why you should take them seriously and respond timely, and what you can do to decrease these incidents on your network.

The danger of spyware is two-fold.   First, it indicates a deficiency on the part of the user in general information security knowledge and specific corporate information security policies.  A spyware infection means that the user likely installed unapproved software on his/her system.  Perhaps the user was doing non-business related web surfing and found the “Totally Awesome Change Your Life Toolbar” from hAcme Software, Inc.  Or maybe the user was tricked into installing this software via social engineering.  (“Click here to install a media player to see Jane E. Celebrity in a bikini!”)  Either way, the user was not aware of the dangers of his/her actions wrt. information security and wrt. corporate security policies.  (You do have policies defining acceptable use of corporate information resources and punishment for misuse, right?)

The second danger (related to the first–in fact, the first is a consequence of the second, so maybe I should have reversed these points–oh well) indicated by a spyware infection is that the user has sufficient rights to execute unapproved software on his/her system that can modify his/her settings and hijack information.  With these rights the user may be delivered and subsequently execute much more damaging malware that exfiltrates personal and/or corporate information or receives and executes instructions from external attackers.  This malware may be delivered by the spyware itself.  Regardless of how it is delivered, your organization has a problem, and it needs to be fixed.

For these two reasons above you should take spyware infections seriously and respond to them in a timely manner.  But what can you do to limit future infections?

1. Limit user rights.  Do not make them a member of the local Administrator or Power Users groups.  If you have applications that require Administrator privileges to run (QuickBooks, I’m looking in your diretion), get rid of them.  That is a poorly designed application and is likely going to have far worse flaws.
2. One word: Education.  Provide it to your users.  If you don’t have a sufficiently trained and knowledgeable employee who can teach one day classes on information security, there are plenty of companies that provide that service–and you won’t have to develop the curriculum.  Google is your friend, here.
3. Follow the hardening guidelines from Microsoft, NIST and NSA on how to secure your Windows systems and networks.
4. Use Group Policy or other enforcement mechanisms available from companies like Cisco, Symantec, etc., to whitelist applications.  Only applications listed in the whitelist can be executed by the user. Use Group Policy to disable all but a few approved Internet Explorer BHOs (Browser Helper Objects).  This will prevent a lot of the toolbar spyware software from infecting your systems.
5. Get serious about your corporate information security posture.  Convince upper management to dedicate sufficient time and money to sustaining a CISO position.

It amazes me that there are some simple firewall rules that everyone can do to aid in the defense of their internal network, yet seem to be rarely implemented.  These rules limit *outbound* traffic.  It seems, unfortunately, many network administrators neglect to limit traffic from their internal network to less-trusted (e.g., VPN, DMZ, and Internet) networks.  Too often this is due to the fact that the admins are too busy trying to keep upper management happy by ensuring that public services (web and e-mail) are accessible to customers and potential customers with five-nines uptime.  This is a sad state of affairs.

How many customers are you really going to lose if your website is down for 5 minutes?  If a customer finds that your website is inaccessible for a short time, they are likely going to first suspect their PC or their ISP network before they blame your organization.  Even if it they do eventually blame you before the problem is resolved, who is really going to be that mad about it?  If Google goes down for 15 minutes (as recently happened), I just chalk it up to bad luck.  I don’t fault Google.  So what, I wasn’t able to hit GMail for 15 minutes?  My life is not over.  Computers suck.  Stuff happens.  Services become inaccessible.  Big deal.

Now, think about how many customers are you going to lose if your organization is in disarray and can’t close sales deals due to some malware spreading internally?  How about your reputation when all your customer information is stolen and posted on the Internet for your competitors (and customers) to see?  What if you lose personal data like SSNs or bank account numbers?  The list of damaging items that can be lost from inside your network is long and scary.  A reasonable person (like myself) would much rather your organization’s Internet services be down for a few minutes (or, heck, even a few hours) than for your organization to lose their confidential data.  Even if you are providing me a service (VoIP or spam filtering, for example), I can stand a few minutes of unexpected downtime (albeit a very few minutes…like 5).  That’s just life.

So enough of the rant.  Here are two simple rules to aid you in detecting malware spreading inside your network.  Of course, you’ll have to be paying some attention to your firewall logs to notice.  You are paying attention, aren’t you?

1. Block outbound SMTP that does not originate from your internal e-mail server(s).
2. Block outbound DNS requests that do not originate from your internal DNS server(s).

Simple.  Quick.  Powerful.  But why are these rules helpful?

The first rule above will catch spambots.  Spambots are malware that sit on a PC and spew tons of spam.  If you have an internal machine spewing e-mail to the Internet, and it’s not your internal mail relay, then that machine is h0sed and you need to examine it.  It’s likely to have more than just one piece of malicious software on it.

The second rule will catch malware that is exploiting the fact that most organizations don’t block outbound DNS.  These malware will use hardcoded public DNS servers to resolve hostnames, all the while avoiding being logged by the legitimate internal DNS server(s).  The hostnames the malware are resolving are often used to aid an attacker in maintaining command and control.

If you can identify infected internal machines through your firewall logs, you can clean the malware and identify further holes in your internal security posture (like foolish users who installed “Whack-a-mole 2009″ from  hAcme Games, Inc., on their corporate PC).