  Current research on users` perspectives of cyber security and privacy related
to traditional and smart devices at home is very active, but the focus is often
more on specific modern devices such as mobile and smart IoT devices in a home
context. In addition, most were based on smaller-scale empirical studies such
as online surveys and interviews. We endeavour to fill these research gaps by
conducting a larger-scale study based on a real-world dataset of 413,985 tweets
posted by non-expert users on Twitter in six months of three consecutive years
(January and February in 2019, 2020 and 2021). Two machine learning-based
classifiers were developed to identify the 413,985 tweets. We analysed this
dataset to understand non-expert users` cyber security and privacy
perspectives, including the yearly trend and the impact of the COVID-19
pandemic. We applied topic modelling, sentiment analysis and qualitative
analysis of selected tweets in the dataset, leading to various interesting
findings. For instance, we observed a 54% increase in non-expert users` tweets
on cyber security and/or privacy related topics in 2021, compared to before the
start of global COVID-19 lockdowns (January 2019 to February 2020). We also
observed an increased level of help-seeking tweets during the COVID-19
pandemic. Our analysis revealed a diverse range of topics discussed by
non-expert users across the three years, including VPNs, Wi-Fi, smartphones,
laptops, smart home devices, financial security, and security and privacy
issues involving different stakeholders. Overall negative sentiment was
observed across almost all topics non-expert users discussed on Twitter in all
the three years. Our results confirm the multi-faceted nature of non-expert
users` perspectives on cyber security and privacy and call for more holistic,
comprehensive and nuanced research on different facets of such perspectives.
