As the others said, egobanks have the best security you can get. I would at the very least assume that: 1. When you upload your backup to the egobank you establish an quantum encryption channel to it, use the channel to create a secure key pair, and then use that to encrypt and send your ego to the egobank. 2. The ego files are encrypted using state of the art crypto. The keys are kept separate and quite possibly in separate parts (there are some nifty protocols that allow shared secrets - there might be five parts of a key, a three or more are needed to unlock the file - so a loss of one or more egobank servers will not prevent restoring the egos). 3. The encrypted ego files have cryptographic checksums that make it very clear if they have been tampered with. 4. The egobank stores several copies in secure locations (if they are really paranoid, they might be using secret sharing on the files too - in order to steal a file you need to steal it from (say) 3 out of 5 locations and merge them). 5. On restoring the file checksums are compared and any discrepancies will ring alarm bells (and if secret sharing is used, this will automatically show up since the patterns do not match). The ego is decrypted, and then send (again with encryption) to a trusted third party resleeving facility. Ok, very reassuring. Now let's think of how this might go wrong. 1. People might allow dangerous code to run in their systems from the start. You want to experience that petal or narcoalgorithm? Oh, you need to give it Administrator access. And people might run various software that has vulnerabilities they ought to have patched, but it is such a hassle... the result is that the virus might get in when they open an email, make a rep update or visit a simspace. And a psychosurgery virus might act on only the backup channel, not the primary brain: the copy that is sent to the egobank is hacked, but the victim doesn't know it until he is restored from backup. 2. Egobanks might not be trusthworthy. Sure, *proper* egobanks are. Cognite Backup Inc, Aeternitas, SecondSelf and Nimbus Ego would stand to loose trillions if they ever had a flaw or mismanaged their customers. Think of how real banks work. But what about the Seventh Heaven Collective on your local scum barge? Or that outfit on Locus you use for your more criminal activities? Even they care about their reputation, but they might be more easily infiltrated, leaned on or just plain criminal. And a surprising number of people trust very untrustworthy people with their lives. Just ask all the people of the Sudanese Government Egobank who found themselves sold to Nine Lives by General al-Fadil... 4. Even if the bank as an organisation is trustworthy there is still a chance that a clever hacker could infiltrate their systems with hacked hardware or software. Very, very hard, but the rewards could be enormous. 5. Also, your resleeving company and their egobridge better be virus free. So, yes, it is entirely possible to hack people with cognoviruses. It is just hard to do it to people who are careful and know what they are doing. But there are enough other people around. In my own game a virus that crudely rewrote the language centres to only handle Mandarin Chinese designed by one of the PCs saved the day when the PCs managed to insert it into the botnet network another mental virus had set up among the brains of the inhabitants of a habitat. But there security had already been breached, of course.

First, don't die. If you don't die, you're not brought up from backup. Second, get an independent party to validate your brain print. Modifications to your brain may be picked up by that. Third, people who are actually important probably get checked regularly by a psychosurgeon for memetic accumulation, psychological disorders, excessive stress, and manipulation. It would turn up on those checks. If it's clearly a virus, it would be documented. Once people figured out it's widespread, everyone who got backed up would be clammoring to get treated, and that backup company would be out of business. There are a few ways to perform a Dollhouse-acolypse. You'd probably want to use them all in tandem. 1) Get the 'independent verifiers' on your side. Get to the people who make the tools. Use that to get false negatives. Get official pronouncements that this neural setting is actually something else. 2) Get in the business not only of running backups, but of memetics, psychosurgery, psychological improvement, skillwires, XPs and anything else that gives you access to unprotected neurons. Introduce the viruses that way. 3) Once you have most of a habitat's backups, destroy that habitat. Insurance covers their morphs and property. When they're brought online, they're all infected. 4) Make the virus self-protecting. The people develop a phobia of brain scans or getting psychoanalyzed. 5) Kill (or buy) the competition to widen your market share. 6) Anarchists are going to be a headache. Get into PR wars with troublesome people. Offer your stuff better freer, but make it too complex for people to bother reverse engineering them. 7) Be ready to move immediately should the virus be discovered.