Dating last referrers
Spammer can fake events, virtual pageviews, screenviews, hostname, request URI, keywords and even transaction and item data: With adequate knowledge of the measurement protocol, it is possible to inflate, deflate or completely delete all of the sales data from any GA property.
A spammer/hacker just needs your GA property ID to do his dirty magic.
They create and send fake referrer headers to avoid being detected as bots.
The fake referrer header contains the website URL which spammer wants to promote and/or build back links.
In fact any person who can benefit financially, in any shape or form, by sending fake traffic can send fake hits to your GA account.
Many SEOs use such spam bots for link building purpose.
Bots are generally used for web indexing (indexing the contents of websites).
But they are also widely used for malicious purposes like: but spam bots don’t.
They can pretend to be traffic coming from a legitimate website.
Not all spam bots are developed to send fake traffic to Google Analytics.