Fear about being "staked out" for robbery is the biggest concern when it comes to rural crime, according to a new report by NFU Mutual.
It says in some places farmers have had to turn their yards into "fortresses" to prevent repeated thefts.
The main targets are four-by-four vehicles, quad bikes, livestock and tools.
The level of crime is down around 15%, but still costs around £3m a year in Northern Ireland.
NFU Mutual spokesman Martin Malone claimed thieves were becoming more brazen and farmers had to constantly increase security to cope.
"They are using tracking devices on tractors, video and infra-red surveillance in their farm yards and even DNA markers to protect sheep from rustlers," he said.
In addition to the fear of being watched, other concerns include longer police response times.
"The threat of becoming a victim of rural crime, and regular reports of suspicious characters watching farms is causing high levels of anxiety amongst farmers who know their rural location makes them vulnerable to attacks," said Mr Malone.
He said the advice was to regularly evaluate security measures, to stay vigilant and report any suspicious activity to police and local farm watch schemes.
The PSNI said its records showed 560 burglary, robbery and theft offences linked to agriculture last year, but the trend was downwards since 2010, when more than 900 such offences were recorded.
Supt Brian McKee, the PSNI's lead on rural and wildlife crime, said police took the issue seriously.
"Agriculture crime represented 1.8% of all burglary, robbery and theft offences, compared with 1.5% during the previous 12 months," he said.
"However this does not diminish the impact these type of crimes have on a rural business, family and community, and we are very mindful of that. It often severely impacts a farm business."