In this lesson,
we're going to be discussing captive portal attacks.
Now, captive portals are commonly used
in public Wi-Fi networks,
such as those in coffee shops, airports, and hotels
to enforce user authentication
or present terms and conditions
before giving somebody access to the internet.
It's important to understand
how captive portal attacks work,
so that you as a penetration tester
can protect against these types of vulnerabilities.
Now, a captive portal is a web page
that users are automatically redirected to
whenever they connect to a public Wi-Fi network.
This page usually requires some form of interaction,
like entering login credentials, accepting terms of service,
or providing an email address
before you as a user can access the internet.
For example, if you're on a United Airlines flight,
a passenger can connect to the in-flight Wi-Fi,
and they'll be redirected to a captive portal.
Here, they might need to log in
with their frequent flier account,
accept the terms of service, or purchase a Wi-Fi pass
before being granted access
to the satellite-based internet on that plane.
Captive portal attacks involve exploiting this mechanism
to intercept the user's credentials,
inject malicious content,
or gain unauthorized access to the network.
Let's break down
some common captive portal attack techniques.
Now, one of the most common techniques
is what's known as an evil twin attack.
In this attack,
the attacker will set up a rogue Wi-Fi access point
that mimics the legitimate network.
The attacker can use the same SSID or network name
and configure this rogue access point with a stronger signal
to lure users into connecting to it
instead of the legitimate network.
Once users connect to the rogue access point,
they're presented with a fake captive portal
that looks identical to the real one.
When users enter their credentials
or other sensitive information,
it will then be captured by the attacker.
For example, if you're at a coffee shop
and see a Wi-Fi network named CoffeeShop WiFi,
an attacker could set up an access point with the same name.
When you connect to the rogue CoffeeShop WiFi,
you'll actually be directed to a fake captive portal
that ask for your login credentials.
If you enter your details,
that attacker now has your information.
Another common technique is to exploit vulnerabilities
in the captive portal software itself.
Many captive portals are built using common web technologies
that have many security flaws like Cross-site Scripting,
SQL injections, or improper session handling.
By exploiting one of these vulnerabilities,
the attacker can bypass the authentication,
inject malicious scripts, or even gain administrative access
to the network infrastructure.
For example, if a captive portal
has a Cross-site Scripting vulnerability,
an attacker could inject malicious JavaScript code
that steals cookies or session tokens from the users
who could connect to the network.
This could allow the attacker
to impersonate legitimate users
and gain unauthorized access to restricted resources.
Now, in a penetration testing scenario,
an attacker might use a captive portal
to gather credentials from unsuspecting users.
For example, the pen tester could set up
a fake captive portal in an airport lounge.
When travelers connect to this network,
they'll be prompted to enter
their frequent flier account details
or accept terms of service on a fake page.
The pen tester will then be able to collect this information
and demonstrate how easy it is for a real attacker
to gather sensitive data from the users.
To protect against captive portal attacks,
an organization needs
to implement several security features.
First, you should always use secure and unique SSIDs
for public Wi-Fi networks,
and avoid using generic names that could easily be spoofed.
Employ a strong encryption mechanism as well like WPA3
with a long, strong password
in order to protect those wireless communications too.
It's also important that you ensure
the captive portal software
is regularly being updated and patched
to address any known vulnerabilities.
You need to conduct regular security assessments
and penetration tests as well
to be able to identify and remediate any weaknesses
in the captive portal's implementation.
Another area of concern
is making sure that you are properly training your users.
User education is really important.
You should encourage your users to verify the authenticity
of the Wi-Fi networks they're going to be connecting to,
and that they should be cautious
whenever they're entering sensitive information
over a public network.
And preferably, they will not be using Wi-Fi,
instead, they should be using a cell phone
or a cell phone hotspot instead.
For example, users should be aware
that legitimate captive portals typically will not ask
for highly sensitive information like banking details
or personal identification numbers.
So remember, captive portal attacks
will exploit the mechanisms used by public Wi-Fi networks
to authenticate their users.
By understanding how these attacks work
and implementing robust security measures,
you're going to be able to protect
your organization and its users
from falling victim to these types of exploits.
Always secure your networks, update your software,
and educate your users
if you want to maintain a strong defense
against captive portal attacks.