Data Breaches and Stock Prices

When talking to companies about the effects of hacking and data breaches I often talk to companies about the effect on stock prices and the potential for brand damage – but, does a security breach really cause a noticeable effect on share prices? Incidentally I was recently working on a script to pull historical stock data for companies at specific dates. So I figured I’d test drive the new script and pull some historic data for companies immediately following a breach, to show the ultra-short term affect on their share price. So I offer my raw data here without analysis and allow you to draw your own conclusions. It’s pretty interesting to see the initial drops in stock and the patterns that affect all companies and all breaches regardless of how well it is handled.

I selected a sample of companies and tried to determine as best as I could the point of disclosure. The point of disclosure is an interesting thing in itself so I’ve tried to pick something sensible, such as the official company disclosure or an early news article. The table below shows, in chronological order, the companies that I ran the number for, their stock code, the date I selected as the “point of disclosure” and a link to the article or official post to add a little depth. I’ve shortened the URLs just to keep the table neat.

Company Name	Stock Code	Disclosure Date	Breach Announcement
Sony PSN	SNE	31-May-11	http://on.mash.to/1NOdh57
Terracom	TER.AX	23-May-13	http://bit.ly/1ONRHxm
Adobe	ADBE	03-Oct-13	http://bit.ly/1CNbsPI
Target	TGT	01-Jan-14	http://tcrn.ch/1VBfWIp
Ebay	EBAY	21-Mar-14	http://bit.ly/1ItoefP
Home Depot	HD	02-Sep-14	http://bit.ly/1qlYRAZ
Google	GOOG	10-Sep-14	http://bit.ly/YxwANL
Sony Pictures	SNE	08-Dec-14	http://bit.ly/1AAFh6e
Premera	ESRX	29-Jan-15	http://bit.ly/22r23NU
Anthem	ANTM	04-Feb-15	http://bit.ly/16kXhba
Experian	EXPN.L	01-Oct-15	http://reut.rs/1U7vSwS
TalkTalk	TALK.L	06-Nov-15	http://bit.ly/1WEWm9d
Juniper	JNPR	17-Dec-15	http://juni.pr/1Zgz2li

The raw data is shown in the following graphs, I’ve included three graphs per company, the first covers a period starting 14 days before the disclosure and 46 days forward, the second is from the point of breach and 14 days forward and the third is from the point of breach and five days forward. So the first figure of each trio will show the point just before the breach where as the second two will show the immediate effect. Each figure includes two views, the top view is a candlestick diagram which shows the open, close, high and low values for each day whist the below view is a simplified one which shows each day’s close value.

My naive view is that the first figure of each trio shows the price trundling along as usual before the point of disclosure where it seems across the board share prices slam down as you’d expect, although surprisingly in many cases the appear to recover very quickly!

Sony PSN