+<!--
+ Copyright © 2021 Soren Stoutner <soren@stoutner.com>.
+
+ This file is part of Privacy Cell <https://www.stoutner.com/privacy-cell>.
+
+ Privacy Cell is free software: you can redistribute it and/or modify
+ it under the terms of the GNU General Public License as published by
+ the Free Software Foundation, either version 3 of the License, or
+ (at your option) any later version.
+
+ Privacy Cell is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with Privacy Cell. If not, see <http://www.gnu.org/licenses/>. -->
+
+<html>
+ <head>
+ <meta charset="UTF-8">
+
+ <link rel="stylesheet" href="../../css/theme.css">
+
+ <!-- Setting the color scheme instructs the WebView to respect `prefers-color-scheme` @media CSS. -->
+ <meta name="color-scheme" content="light dark">
+ </head>
+
+ <body>
+ <p><a href="https://en.wikipedia.org/wiki/IMSI-catcher">IMSI catchers</a>, also known as stingrays, are fake cell phone towers that intercept your traffic and spy on you.
+ Each generation of cell phone protocols has attempted to mitigate stingrays, but each has generally failed.
+ With 5G, more of the traffic is encrypted in such a way that it prevents stingray spying.
+ However, 5G networks can run in a blended 4G/5G mode, where the control channel is 4G and the data channel is 5G.
+ This is known as <a href="https://en.wikipedia.org/wiki/5G_NR#Non-standalone_mode">5G NR NSA</a> (5G New Radio Non-Standalone) mode.
+ When connected to such a blended network, a cell phone is not protected against
+ <a href="https://www.wired.com/story/5g-network-stingray-surveillance-non-standalone/">modern stingray attacks</a>.</p>
+
+ <p>The Android status bar does not differentiate between 5G modes. It will display the same 5G icon for Standalone and Non-Standalone networks.
+ The purpose of Privacy Cell is to make it easy to tell what type of network you are connected to.
+ If you are in an area where you usually are connected to a <a href="https://en.wikipedia.org/wiki/5G_NR#Standalone_mode">5G NR SA</a> network and Privacy Cell shows a 5G NR NSA connection,
+ it is possible that a stingray has performed a downgrade attack to spy on your communications.</p>
+
+ <p>It should be noted that paltry attempts have been made to secure cell phone protocols in the past, which have never been sufficiently well designed to provide real protection.
+ Even if you are connected to a 5G NR SA network, it is likely that there are still unknown weaknesses in the network that can be exploited by a sufficiently funded adversary.
+ Privacy Cell will be updated regarding these types of vulnerabilities as future research identifies them.</p>
+ </body>
+</html>
\ No newline at end of file