Web Shells: The Criminal’s Control Panel

Web shells are an overlooked aspect of cyber crime and do not attract the level of attention of either phishing or malware. Nevertheless, Netcraft found more than 6,000 web shells during April 2017, which works out at around 1 new shell installation every 5 minutes. When web shells first appeared, the limit of their functionality was to transfer files and execute arbitrary shell commands. However, the best engineered web shells now provide well presented, sophisticated toolkits for diverse crimes, with facilities for password cracking, privilege elevation, network reconnaissance, phishing, spamming and DDoS, not solely available through a web based user interface but also accepting commands as part of a botnet.

An example of the WSO shell

An example of the hugely popular and feature-rich WSO (Web Shell by Orb) shell.

A number of shells offer the creation of a botnet in as little as a click, launching standalone processes that either connect to a command and control server or listen for commands over an insecure TCP connection. Some allow performing port scans to find potentially exploitable services. Others enable fraudsters to schedule denial of service attacks. There are shells dedicated to sending bulk spam emails, testing stolen credentials against popular websites (such as PayPal or Amazon), cracking passwords, and automatically defacing websites. With such a wide array of powerful features, it is unsurprising how popular web shells are with cyber criminals.

The WSO shell offers both bind shell and back connect options. Selecting one of these options will launch a standalone process that will connect to or listen for a connection from a remote command and control server - an easy method for the creation of a botnet.

WSO offers both bind shell and back connect options. Selecting one of these options will launch a standalone process that will connect to or listen for a connection from a remote command and control server - an easy method for the creation of a botnet.

The prevalence of these backdoors allows easy—and potentially persistent—access to thousands of compromised machines. If the web shell is missed during the webmaster's cleanup after an attack, removing the original phishing or malware content will be in vain, as the fraudster can use the web shell to upload new malicious material, or re-purpose the machine as an accessory to alternative forms of cyber crime.

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Phishing sites react promptly to new browser changes

The number of phishing sites making use of HTTPS has increased noticeably since January, coinciding with the introduction of a new feature in the Mozilla Firefox and Google Chrome web browsers.

Both Firefox and Chrome now display warnings when an unencrypted (HTTP) webpage contains a password field. This behaviour is intended to protect users from man-in-the-middle attacks, and also encourages the affected websites to start using secure HTTPS connections when handling sensitive data.

This German PayPal phishing site uses the unencrypted HTTP protocol, causing the latest version of Firefox to display an unmissable warning message when the user interacts with the login form.

This German PayPal phishing site uses the unencrypted HTTP protocol, causing the latest version of Firefox to display an unmissable warning message when the user interacts with the login form.

These warning messages could scupper many phishing sites: Most are served over unencrypted HTTP connections, and so another positive consequence of the new browser behaviour is that potential victims are less likely to fall for phishing attacks.

However, fraudsters may have quickly realised this, as there has been a dramatic increase in the number of phishing sites making use of HTTPS. If the new browser behaviour has driven this change — and the timing suggests it might have — then it may have also had the unintended side effect of increasing the efficacy of some phishing sites. Phishing sites that now use HTTPS and valid third-party certificates can appear more legitimate, and therefore increase the likelihood of snaring a victim.

Firefox 51 and Chrome 56 were the first stable browsers to flag HTTP websites as insecure if they contained password fields. Their release dates appear to coincide with the increase in HTTPS phishing sites.

Firefox 51 and Chrome 56 were the first stable browsers to flag websites as insecure if they contained password fields. Their release dates appear to coincide with the increase in HTTPS phishing sites.

Another plausible hypothesis is that many legitimate websites have migrated to HTTPS in response to the new behaviour in Firefox and Chrome. Phishing sites are often hosted on compromised websites, and so this would naturally cause the number of HTTPS phishing sites to increase accordingly; or it could be that some fraudsters are now targeting HTTPS websites in preference to HTTP sites.

While the majority of today's phishing sites still use the unencrypted HTTP protocol, a threefold increase in HTTPS phishing sites over just a few months is quite significant. Regardless of what caused this change, phishing sites that use the unencrypted HTTP protocol could still prove effective against some victims, as not all browsers share the behaviour implemented in Firefox and Chrome. In particular, Microsoft's Internet Explorer and Edge browsers do not yet display any warnings when users interact with insecure forms.

Panama’s abundance of phish!

According to tradition, the country of Panama was named after a former indigenous fishing village and its nearby beach called Panamá, meaning "an abundance of fish"; but today, it looks like Panama has an abundance of phish!

Netcraft has blocked nearly 5,000 phishing sites in Panama over the past three months, which is an astounding amount considering Panama hosts fewer than 13,000 active websites in total.

Nearly 4,000 phishing sites are still blocked, making Panama the phishiest country in the world at the present moment. To give these figures some perspective, only 0.007% of the world's active sites are hosted in Panama, yet it hosts 1.0% of all phishing sites that are currently blocked.

An Apple ID phishing site currently hosted by Offshore Racks in Panama.

An Apple ID phishing site currently hosted by Offshore Racks in Panama.

Around 1.9 million people are estimated to use the internet in Panama, but most of the phishing sites hosted there are clearly aimed at foreigners, as the majority are not written in Panama's official language of Spanish. In fact, most of the currently blocked phishing sites target customers of Italian banks, and a large proportion of new phishing sites found in Panama over the past month were written in English and targeted Apple customers.

Most of the Apple phishing attacks make use of domain names that have been registered specifically to carry out these attacks, with many containing obvious references to Apple, Apple ID, or iCloud.

A handful of the domains used by Apple phishing attacks last month.

A few examples of the domains used by Apple phishing attacks last month.

The majority of these phishing sites are hosted by Offshore Racks, a Panamanian hosting company that offers "high privacy" anonymous hosting and accepts payment in Bitcoins – ideal for fraudsters who do not want to be traced easily.

As the phishing sites make use of domain names that have been registered specifically for phishing, this suggests the fraudsters have purposely sought their own hosting arrangements, rather than adopting the more common method of deploying phishing kits on compromised web servers. While this eliminates the risk of the phishing content being deleted by the disgruntled owner of a compromised site, the obvious disadvantage for the fraudster is that he may have to pay for both domain registrations and hosting.

Offshore Racks' Acceptable Use Policy has said nothing more than "In development" since 2010

Offshore Racks' Acceptable Use Policy has said nothing more than "In development..." since 2010.

While it is clear that the company responsible for hosting most of these phishing sites could be doing more to prevent the attacks, domain name registrars and domain registries are also well positioned to nip this activity in the bud. Netcraft's Deceptive Domain Score service can be used to analyse the likelihood of a domain name being used for fraudulent activities, giving an opportunity to prevent the registration, flag for human inspection, or immediately suspend fraudulent domains, before malicious content can be uploaded. Domains that have already been registered can be suspended by TLD operators as soon as phishing activity is detected.

Consumers can boost their browsers' standard security features by installing the Netcraft anti-phishing extension. As well as blocking access to known phishing sites, it will display the hosting location, Risk Rating and other information that can help establish the authenticity of every site visited.

Hotpoint service sites hacked

Hotpoint's UK service website has been hacked. Instead of allowing customers to activate warranties, book services or find an engineer, the site is currently putting its customers at risk by redirecting them to a variety of dubious websites.

Some visitors were presented with a fake Java update page, which downloaded malware.

Some Hotpoint visitors are being redirected to a fake Java update page, which downloads malware.

The hacker has accomplished this feat by appending malicious JavaScript code to several of the scripts hosted on the Hotpoint service site. It was not readily apparent how the hacker gained write-access to these files, but the WordPress content management system that the site runs on is notorious for being compromised if both it and its plugins are not kept up to date.

The hack has also affected Hotpoint's Irish service website, which is hosted on the same IP address as the UK one.

The malicious code appended by the attacker. This appears at the end of an otherwise-legitimate script which asks the user whether they want to accept cookies from the site

The malicious code appended by the attacker. This appears at the end of an otherwise-legitimate script which asks the customer whether they want to accept cookies from the site.

The appended code is obfuscated to make its purpose less apparent, perhaps in the hope that nobody would dare to delete it. De-obfuscating the code reveals that it is responsible for loading a larger obfuscated script from an external site.

The externally hosted malicious script pretends to be an innocuous jQuery file; but scrolling down reveals its true content, which is obfuscated.

The externally hosted malicious script pretends to be an innocuous jQuery file; but scrolling down reveals its true content, which is obfuscated.

Presumably, this external site is operated by the hacker, in which case he has the opportunity to change the content of his malicious payload at will. Any visitor to the Hotpoint service site could consequently be at risk of much more serious attacks, such as drive-by malware or phishing.

Hotpoint service customers are also being redirected to scam survey sites like this one.

Many bank holiday shoppers who buy Hotpoint white goods are likely to fall victim to this attack, as the paperwork included with new appliances directs new customers to the site to activate their 10 year parts guarantee.

Thanks Tim

New customers are directed to the hacked site.

Existing customers desperate to find out about certain models of dangerous tumble dryers are also likely to be snared by the JavaScript attack.

Generally, the Easter bank holiday weekend is a good time for hackers to strike UK websites, as many people will be on holiday on both Good Friday and the following Monday. The longer the attacker can keep his redirection code in place, the more revenue he can reap.

Of course, there could be wider-reaching repercussions to this attack – if an attacker has been able to modify scripts on Hotpoint's website, then he could also have been in a position to view any data stored or transmitted by the site.

Let’s Encrypt and Comodo issue thousands of certificates for phishing

Update: This article was published in April 2017. Up-to-date statistics on TLS certificates used for phishing can be found at Netcraft's Phishiest Certificate Authorities page.

Certificate Authorities are still issuing tens of thousands of certificates for domain names obviously intended for use in phishing and fraud. Fraudsters are mostly using just two CAs — Let's Encrypt and Comodo domain-validated certificates accounted for 96% of phishing sites with a valid TLS certificate found in the first quarter of 2017.

Netcraft has blocked phishing attacks on more than 47,500 sites with a valid TLS certificate between 1st January and 31st March 2017. On 19,700 of these, Netcraft blocked the whole site rather than a specific subdirectory. 61% of the sites that were entirely blocked were using certificates issued by Let's Encrypt, and 36% by Comodo.

While some CAs, browser vendors, and commentators have argued that fraud prevention is not and should not be the role of certificate authorities, the scale of foreseeable misuse that can be combated automatically warrants further consideration of this policy. Without change, issuance of certificates for sites such as login-appleid.com-direct-apple.com and dropbox.com.login.verify.danaharperandfriends.com that are obviously intended for misuse will continue unabated.

Certificates issued by publicly-trusted CAs that have been used on phishing sites

Certificates issued by publicly-trusted CAs that have been used on phishing sites. An interactive, updating version of this graph can be found on Netcraft's Phishiest Certificate Authorities page.

Mozilla Firefox's telemetry reports that approximately 55% of all page loads are over HTTPS. The movement to a secure web is crucial to defend against the risks posed by unencrypted traffic, and easy access to trusted certificates is a key factor in the recent growth. However, this easy access also offers opportunities for fraudsters to capitalise on the perception of HTTPS as trustworthy as demonstrated by the number of certificates issued for clearly deceptive domain names.

Looking at a small sample of these blocked phishing sites with valid TLS certificates that have high Deceptive Domain Scores:

Hostname Certificate Authority Target Deceptive Domain Score
login-appleid.com-direct-apple.com Let's Encrypt Apple
9.25
payepal.com-signin-country-localed.access-logons.com Let's Encrypt PayPal
9.13
www.ll-airbnb.com Symantec Airbnb
8.99
chaseonline.chase.com.bajpayee.com Comodo Chase
10.00
payqal.limited GoDaddy PayPal
9.13
lost-apple.ru GlobalSign Apple
9.30
servicesonline-americanexpress.com Let's Encrypt American Express
7.99
dropbox.com.login.verify.danaharperandfriends.com Comodo Dropbox
9.70
update.wellsfargo.com.casaecologica.cl Let's Encrypt Wells Fargo
10.00
bankofamerica.com.online.do.dbraunss.org Comodo Bank of America
9.40
labanque-postalegroupe.com Let's Encrypt La Banque Postale
7.10
usaa.com.983746.imexcomed.com.bo Let's Encrypt USAA
10.00

In each of these examples above — and in the other statistics referenced above — the certificate authority had sight of the whole hostname that was blocked. These examples did not rely on wildcard certificates to carry out their deception. In particular, some of these examples (such as update.wellsfargo.com.casaecologica.cl) demonstrate that the certificate authority was better placed to prevent misuse than the domain registrar (who would have seen casaecologica.cl upon registration).

Let's Encrypt and Comodo are attractive to fraudsters as both offer automated, domain-validated certificates at no cost to end users. Let's Encrypt's ACME protocol allows for free automated issuance, while Comodo offers no-cost certificates via its trial certificates, cPanel AutoSSL, and its Cloudflare partnership.

While Let's Encrypt's policy on phishing and malware is to check the Safe Browsing API, this does not provide effective pre-issuance blocking. It does not match the reality of automated certificate deployment, where the certificate is likely to be issued and installed before the phishing content has been uploaded, detected, and blocked. Let's Encrypt also has a limited list of domain names for which they block issuance which has triggered forum posts by users unable to obtain a certificate for the blocked name. All of the Let's Encrypt certificates that Netcraft found on phishing sites were issued despite the Safe Browsing check and the additional name-based blocking.

Phishing site on https://www.instagram.com-getid.com

Phishing site on https://www.instagram.com-getid.com (Deceptive Domain Score is 9.46).

The use of TLS by these phishing sites is particularly dangerous, as websites that use TLS are marketed as being trustworthy and operated by legitimate organisations. Consumers have been trained to look for padlocks, security indicators, and https:// in the address bar in their browser before submitting sensitive information, such as passwords and credit card numbers, to websites.

However, a displayed padlock or "Secure" indicator alone does not imply that a site using TLS can be trusted, or is operated by a legitimate organisation. The distinction between the connection being "Secure" and the safety of providing sensitive information to the HTTPS site may be challenging to interpret for those unfamiliar with the technical underpinnings of TLS.

"Secure" vs. "Private" in Google Chrome

"Secure" vs. "Private" in Google Chrome.

Demonstrating the difficulty of explaining this technical distinction, Google Chrome indicates that an HTTPS connection is using a valid TLS certificate by displaying the word "Secure" in the address bar. While the word "secure" refers to the encrypted connection's protection against eavesdroppers, this is explained in the drop-down with the word "private". The distinction between these two words is subtle, yet potentially significant for user understanding. However, it is important to note that Google has been at the forefront of research into how security indicators are perceived by internet users at large.

Mozilla Firefox's warning when selecting a password form field on a non-secure HTTP site

Mozilla Firefox's warning when selecting a password form field on a non-secure HTTP site.

Both Google Chrome and Mozilla Firefox have made recent changes to the display of password input forms on non-TLS sites — non-secure forms now trigger in-context warnings. These warnings are likely to increase the prevalence of TLS on phishing sites, with fraudsters deploying TLS to both gain the positive "Secure" indicator, and now to avoid negative indicators when collecting passwords.

Deceptive Domain Score service

Netcraft's Deceptive Domain Score service provides an automated mechanism for evaluating whether a given hostname or domain name is likely to be used to fraudulently impersonate an organisation. Crucially, this can be evaluated before issuing a certificate. Of these 19,700 hostnames with valid TLS certificates where Netcraft blocked the entire site, 72.5% scored more than 5.0 and 49% more than 7.0 (on a scale from 0.0 to 10.0).

Distribution of Deceptive Domain Score across blocked phishing sites with valid TLS certificates

Distribution of Deceptive Domain Score across blocked phishing sites with valid TLS certificates.

For comparison, a random sample of 10,000 hostnames taken from domain-validated certificates issued in February 2017 as found in Netcraft's April 2017 SSL survey, had an average score of 0.72, with 7% having a score over 5.0, and 4.4% a score over 7.0.

More information on Netcraft's Deceptive Domain Score service can be found on Netcraft's website.

Government websites pair up to host Apple ID phishing attack

Brazilian and Laotian government websites were found collaborating in an unusual Apple ID phishing attack today.

The Brazilian government education WordPress site at http://ead.go.gov.br/, and the Laotian government Department of Posts and Telecommunications site at https://dpt-km.gov.la — which runs Joomla — have evidently been compromised in this attempt to steal Apple ID credentials.

A subdirectory on http://ead.go.gov.br/ houses this phishing content, which prompts victims to enter their Apple IDs and passwords.

A subdirectory on http://ead.go.gov.br/ houses this phishing content, which prompts victims to enter their Apple IDs and passwords.

The most unusual thing about this particular incident is that both government sites are being used to carry out the same phishing attack: The spoof Apple ID login form is hosted on the Brazilian government site, while the Laotian government site hosts a script that redirects visitors to the spoof form on the Brazilian site.

In a separate spate of attacks, an Alibaba phishing site was also discovered on another Brazilian government site this week at http://cmrn.mg.gov.br, and a LinkedIn phishing site was found on the Pakistani government health information website at http://dhiskp.gov.pk/. The Laotian government site was also used to host a redirect to another phishing attack against a Greek bank last month.

While it is common for phishing sites to be hosted on compromised web servers, it is often assumed that government websites would be more secure than average; but this is not always the case, as empirically demonstrated by this week's attacks, and also by previous attacks hosted on Malaysian, Nigerian and Thai government websites.

However, this is the first time Netcraft has seen two different governments' websites working together to take part in the same phishing attack.