Under normal circumstances, a Cortical Stack is a "write-only" device, which is deliberately isolated from most other data connections and storage to take only the neural network snapshots required for a backup. They can only be read using specialized equipment which is very expensive, and in many cases not portable. Even so, Even so, some people are worried about others having access to their stack in case they die or are killed. This has led to a proliferation of security measures, like Dead Switches, False Deaths, Self-Destructs, autodelete or copy-protection software and more. But for some, there are simpler solutions, though they have their own ups and downs.
Stack Encryption: This implant overhauls the cortical stack storage medium and it's underlying software, encoding brainscans in simple but hard to break encryption to prevent unauthorized users from reading the stack. The key to this encryption is usually held by a backup service, offsite data security, or with passwords/keys in the possession of the user (which means if you kill someone to take their stack, you can't get the password). A morph with Stack Encryption enabled gives a -30 penalty to Psychosurgery attempts to access or edit the backup data on the stack, and similar penalties to any InfoSec/Interfacing tests to tamper with the stack while still hooked up in a morph unless they have authorized access (or take time to break the encryption with a Quantum Codebreaking Computer). Normally this can only be installed in a morph with a Cortical Stack, but infomorphs may also take this as a Software Plugin which encrypts and obfuscates ego data recorded on a server - but would require another plugin like Emergency Backup (p. 140 Transhuman) to work. [Moderate]
Most insurance companies and several governments with resleeving programs actually ban or carefully regulate Stack Encryption because it harms their ability to do their job, and one often has to pay higher premiums on a Backup Insurance contract if your stack is to be encrypted and the company to store the authorization data. More security focused governments also ban this as part of their efforts to promote public safety - as it is very hard to interview someone in case of an accident or crime if their stack cannot be read. On the other hand, Covert Operatives engaging in risky operations may prefer encryption to Dead Switches or highly expensive emergency farcasters or QE comms - as the encryption can be held by their home agency and used to recover intel or egos if they are lost.