Posté par: igor51 le février 07, 2018, 19:00:30
Social Engineering and Two-Factor Authentication
Social engineering campaigns are a constant threat to businesses
because they target the weakest chain in security: people. A typical
attack would capture a victim’s username and password and store it for
an attacker to reuse later. Two-Factor Authentication (2FA) or
Multi-Factor Authentication (MFA) is commonly seen as a solution to
these threats.
2FA adds an extra layer of authentication on top of the typical
username and password. Two common 2FA implementations are one-time
passwords and push notifications. One-time passwords are generated by
a secondary device, such as a hard token, and tied to a specific user.
These passwords typically expire within 30 to 60 seconds and cannot be
reused. Push notifications involve sending a prompt to a user’s mobile
device and requiring the user to confirm their login attempt. Both of
these implementations protect users from traditional phishing
campaigns that only capture username and password combinations.
Real-Time Phishing
While 2FA has been strongly recommended by security professionals
for both personal and commercial applications, it is not an infallible
solution. 2FA implementations have been successfully defeated using
phishing techniques. These phishing attacks involve interaction
between the attacker and victims in real time.
A simple example would be a phishing website that prompts a user for
their one-time password in addition to their username and password.
Once a user completes authentication on the phishing website, they are
presented with a generic “Login Successful” page and the one-time
password remains unused but captured. At this point, the attacker has
a brief window of time to reuse the victim’s credentials before expiration.
Social engineering campaigns utilizing these techniques are not new.
There have been reports of
phishing in the wild as early as 2010. However, these types of
attacks have been largely ignored due to the perceived difficulty of
launching such attacks. This article aims to change that perception,
bring awareness to the problem, and incite new solutions.
Explanation of Tool
To improve social engineering assessments, we developed a tool –
named ReelPhish –
that simplifies the real-time phishing technique. The primary
component of the phishing tool is designed to be run on the attacker’s
system. It consists of a Python script that listens for data from the
attacker’s phishing site and drives a locally installed web browser
using the Selenium framework.
The tool is able to control the attacker’s web browser by navigating
to specified web pages, interacting with HTML objects, and scraping content.
The secondary component of ReelPhish resides on the phishing site
itself. Code embedded in the phishing site sends data, such as the
captured username and password, to the phishing tool running on the
attacker’s machine. Once the phishing tool receives information, it
uses Selenium to launch a browser and authenticate to the legitimate
website. All communication between the phishing web server and the
attacker’s system is performed over an encrypted SSH tunnel.
Victims are tracked via session tokens, which are included in all
communications between the phishing site and ReelPhish. This token
allows the phishing tool to maintain states for authentication
workflows that involve multiple pages with unique challenges. Because
the phishing tool is state-aware, it is able to send information from
the victim to the legitimate web authentication portal and vice versa.
Examples
We have successfully used ReelPhish and this methodology on numerous
Red Team engagements. The most common scenario we have come
across is an externally facing VPN portal with two-factor
authentication. To perform the social engineering attack, we make a
copy of the real VPN portal’s HTML, JavaScript, and CSS. We use this
code to create a phishing site that appears to function like the original.
To facilitate our real-time phishing tool, we embed server-side code
on the phishing site that communicates with the tool running on the
attacker machine. We also set up a SSH tunnel to the phishing server.
When the authentication form on the phishing site is submitted, all
submitted credentials are sent over the tunnel to the tool on the
attacker’s system. The tool then starts a new web browser instance on
the attacker’s system and submits credentials on the real VPN portal.
Figure 1 shows this process in action.
Figure 1: ReelPhish Flow Diagram
We have seen numerous variations of two-factor authentication on VPN
portals. In some instances, a token is passed in a “secondary
password” field of the authentication form itself. In other cases, the
user must respond to a push request on a mobile phone. A user is
likely to accept an incoming push request after submitting credentials
if the phishing site behaved identically to the real site.
In some situations, we have had to develop more advanced phishing
sites that can handle multiple authentication pages and also pass
information back and forth between the phishing web server and the
tool running on the attacking machine. Our script is capable of
handling these scenarios by tracking a victim’s session on the
phishing site and associating it with a particular web browser
instance running on the attacker’s system. Figure 1 shows a general
overview of how our tool would function within an attack scenario.
We are publicly releasing the tool on the
Repository. Feedback, pull requests, and issues can also be
submitted to the Git repository.
Conclusion
Do not abandon 2FA; it is not a perfect solution, but it does add a
layer of security. 2FA is a security mechanism that may fail like any
other, and organizations must be prepared to mitigate the impact of
such a failure.
Configure all services protected by 2FA to minimize attacker impact
if the attacker successfully bypasses the 2FA protections. Lowering
maximum session duration will limit how much time an attacker has to
compromise assets. Enforcing a maximum of one concurrent session per
user account will prevent attackers from being active at the same time
as the victim. If the service in question is a VPN, implement strict
network segmentation. VPN users should only be able to access the
resources necessary for their respective roles and responsibilities.
Lastly, educate users to recognize, avoid, and report social
engineering attempts.
By releasing ReelPhish, we at Mandiant hope to highlight the need
for multiple layers of security and discourage the reliance on any
single security mechanism. This tool is meant to aid security
professionals in performing a thorough penetration test from beginning
to end.
During our Red Team engagements at Mandiant, getting into an
organization’s internal network is only the first step. The tool
introduced here aids in the success of this first step. However, the
overall success of the engagement varies widely based on the target’s
internal security measures. Always work to assess and improve your
security posture as a whole. Mandiant provides a variety of services
that can assist all types of organizations in both of these activities.
Source: ReelPhish: A Real-Time Two-Factor Phishing Tool (http://)