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Gaps in corporate network security: ad networks

Malware Alerts - Fri, 09/05/2014 - 09:42

'Malvertising' is a relatively new term for a technique used to distribute malware via advertising networks, which have long since become a popular medium among cybercriminals. In the past four years, hundreds of millions of users have fallen victim to 'viral' advertising, including visitors to major media sites, such as NY Times, London Stock Exchange, Spotify, USNews, TheOnion, Yahoo!, and YouTube. The complicated situation with ad networks even prompted the United States Senate Permanent Subcommittee on Investigations to conduct an in-depth inquiry, which produced recommendations on stepping up security and increasing the responsibilities of advertising platform owners.

At the turn of the year 2.5 million Yahoo users were attacked. Soon after the incident, a company called Fox IT published a detailed analysis of the attack. Curiously, according to Fox IT, not all Yahoo! users were affected by the attack – only residents of European countries, primarily Romania, the UK and France. Fox IT analysts believe that the attackers probably used targeted advertising mechanisms, i.e., they paid for 'impressions' served to a certain audience from the countries mentioned above. Here is an illustration of how attacks are conducted via ad networks: an overall attack organization diagram (on the left-hand side) and a specific example of the attack against Yahoo! users (on the right-hand side).

In the past, we have written about targeted attacks conducted via trusted websites (so-called watering-hole attacks) and social engineering on social networks and in IM clients. Specifically, we wrote that a cybercriminal has to do two things in order to implement a watering-hole attack: first, compromise a trusted website and second, surreptitiously inject malicious scripts into the site's code. Successful attacks via social networks or IM clients also make certain demands of cybercriminals – at the very least, to win the users' trust and increase the chances of them clicking on links sent by the attackers.

What sets attacks via ad networks apart is that in these attacks the cybercriminals do not have to compromise websites or gain the trust of potential victims. All they have to do is find an ad provider from which to buy 'impressions' or become a provider themselves (like BadNews). The remaining work, related to distributing malicious code, will be done by the ad network –the trusted site itself will download malicious scripts to its page via iframe.

Moreover, users don't even have to click on the ads – as part of its attempt to display a banner on the web page, the browser executes the banner's SWF/JS code, which automatically redirects the user to a site hosting the landing page of a popular exploit pack, such as Blackhole. A drive-by attack will follow: the exploit pack will attempt to choose an appropriate exploit to attack a vulnerability in the browser or its plugins.

The problem of ad networks being used to distribute malware and conduct targeted attacks (taking advantage of their targeted advertising capabilities) does not only affect those who use browsers to access websites. It also applies to users of applications that can display adverts, such as IM clients (including Skype), email clients (Yahoo! included), etc. And, most importantly, the problem affects the huge number of mobile app users, since these apps also connect to ad networks!

Essentially, mobile applications are different in that the SDKs commonly used for embedding adverts into apps (such as AdMob, Adwhirl etc.) do not support the execution of arbitrary code supplied by ad providers, as is the case with website advertising. In other words, only static data is accepted from the server supplying ads, including images, links, settings etc. However, cybercriminals can also create SDKs, just like media companies. The former offer developers higher per-click rates than their legitimate competitors. This is why developers of legitimate mobile software embed malicious 'advertising' code – essentially backdoors – into their apps. Moreover, legitimate SDKs may have vulnerabilities enabling the execution of arbitrary code. Two such cases were identified late last year – one involving the HomeBase SDK, the other involving AppLovin SDK.

Source: http://researchcenter.paloaltonetworks.com

The question "How should a corporate network be protected against attacks conducted via ad networks?" does not have a simple answer, particularly if you keep in mind possible targeted attacks. As we mentioned before, protection needs to cover not only workstations (browsers, IM clients, email clients and other applications that have dynamic advertising built into them), but also mobile devices that can access the corporate network.

Clearly, protecting workstations requires at least a Security Suite class anti-malware solution, which must include:

  • protection against vulnerability exploitation;
  • advanced HIPS with access restriction features, as well as heuristic and behavioral analysis (including traffic analysis);
  • tools for monitoring the operating system (System Watcher or Hypervisor) in case the system does get infected.

For more reliable protection of workstations, it is prudent to use application control technology, collect statistics (inventory) on the software used on the network, set up updating mechanisms and enable Default Deny mode.

Unfortunately, compared to the protection of workstations, mobile device protection is still in the early stages of evolution. It is extremely difficult to implement a full-scale Security Suite or Application Control solution for mobile devices, since that would require modifying firmware, which is not always possible. This is why Mobile Device Management (MDM) technology is currently the only effective tool for protecting mobile devices that connect to the corporate network. The technology can control which applications are allowed to be installed on a device and which are not.

Cybercriminals have used ad networks to distribute malware for years. At the same time, the advertising market is rapidly growing, branching out into new platforms (large websites, popular applications, mobile devices), attracting new advertisers, partners, intermediaries and aggregators, which are intertwined into an extremely tangled network. The ad network problem is one more example showing that rapid technology development is not always accompanied by the corresponding evolution of security technologies.

Protecting yourself against the celebrity iCloud hackers

Malware Alerts - Wed, 09/03/2014 - 15:51

The biggest security news of the week is the leaked photos of many celebrities. Many people, especially the involved celebrities, wondered how such a hack could take place.

The initial statement by the attacker was that the iCloud was hacked. This prompted Apple into their we-do-not-really-comment-until-we-have-done-our-research mode. Today, they released a statement on the incident:

https://www.apple.com/pr/library/2014/09/02Apple-Media-Advisory.html

For me the most interesting quote is: “accounts were compromised by a very targeted attack on user names, passwords and security questions, a practice that has become all too common on the Internet.”

Apple is thus well aware of the problems that arise with these forms of authentication. The more interesting is their advice: strong passwords and two-step-verification.

Strong passwords are, according to Apple, passwords with a minimum of 8 characters, with some additional requirements. Interesting enough they do not enforce of all their suggestions. A password such as “Password1″ is acceptable, even though it can be easily guessed.

Their other advice, using two-factor-authentication is somewhat flawed. For instance, it does not protect your iCloud backups (see this post). Also, two-step-verification is not available in every country. If you use, for example, a Romanian or a Croatian telephone number, then bad luck. Considering that Google offers two factor authentication for such countries as well, one might wonder why Apple didn’t implement it as well. Could it be the cost of the SMSes?

So how to protect yourself properly? My colleague Alex Savitsky wrote an excellent article about this.

To summarize:

  • Use strong and unique passwords that are easy to remember and hard to crack (for instance, a phrase in your native language with “spaces” in it, a number and a special char)
  • If available in your country, enable two-factor authentication
  • iPhone users may want to disable iCloud photo Stream / photo Sharing. Additionally iPhone users may want to delete the backup of their photos / iPhone in the iCloud.

Photo courtesy of my colleague Dmitry Bestuzhev – https://twitter.com/dimitribest/status/506820178320322560

And remember – if you don’t want your private photos to get leaked, better not take them in the first place!

Web-based attack targeting home routers, the Brazilian way

Malware Alerts - Tue, 09/02/2014 - 14:53

We spotted an interesting attack from Brazilian bad guys aiming to change the DNS settings of home routers by using a web-based attack, some social engineering, and malicious websites. In these attacks the malicious DNS servers configured in the user's network device are pointed towards phishing pages of Brazilian Banks, programmed to steal financial credentials.

Attacks targeting home routers aren't new at all; in 2011, my colleague Marta described malware targeting network devices like these. In Brazil we documented a long and painful series of remote attacks that started in 2011-2012 that affected more than 4.5 million DSL modems, exploiting a remote vulnerability and changing DNS configurations. But this "web-based" approach was something new to Brazilian bad guys until now and we believe it will spread quickly amongst them as the number of victims increases.

The attack starts with a malicious e-mail and a bit of social engineering, inviting you to click:

"I'm your friend and want to tell you you're being cheated, look at the pics"

How many people believe in it? Well, many: 3.300 clicks in 3 days, with most of the users located in Brazil, US and China, probably Brazilians living there or people that understand Portuguese:

Shortened URLs are a cheap way for the bad guy measure their 'performance'

The website linked in the message is full of adult content, porn pics. While in the background it starts running scripts. Depending on your configuration, at some point the website may ask for the username and password of your wireless access point – if it has, this is a good thing. If not, this may be a problem for you:

The script located in the website will try to guess the password of your home router. It tries several combinations such as "admin:admin":

or "root:root"

or "admin:gvt12345" (GVT is a big Brazilian ISP):

The scripts will continue trying combinations that point to the control panel of your network device such as [your-router-IP].rebootinfo.cgi or [your-router-IP].dnscfg.cgi?. Each script includes the commands to change the primary and secondary DNS servers. If you're using default credentials in your home router, there won't be an interaction and you'll never realize that the attack has occurred. If you're not using default credentials, then the website will pop up a prompt asking you to enter it manually.

We found Brazilian bad guys actively using 5 domains and 9 DNS servers – all of them hosting phishing pages for the biggest Brazilian Banks. The malicious websites used in the attacks are filtering direct access by using HTTP referrers, thus aiming to prevent direct access from security analysts.

So how do you protect yourself? Make sure you're not using the default password in your home router and NEVER enter your credentials into any website asking for them. Our Kaspersky Internet Security is also prepared to block such scripts automatically.

 

Know your IMEI?

SANS Tip-of-the-Day - Mon, 09/01/2014 - 22:49

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