There has been a huge spike in the usage of social media platforms during the COVID-19 lockdowns. These lockdown periods have resulted in a set of new cybercrimes, thereby allowing attackers to victimise social media users with a range of threats. This paper performs a large-scale study to investigate the impact of a pandemic and the lockdown periods on the security and privacy of social media users. We analyse 10.6 Million COVID-related tweets from 533 days of data crawling and investigate users' security and privacy behaviour in three different periods (i.e., before, during, and after the lockdown). Our study shows that users unintentionally share more personal identifiable information when writing about the pandemic situation (e.g., sharing nearby coronavirus testing locations) in their tweets. The privacy risk reaches 100% if a user posts three or more sensitive tweets about the pandemic. We investigate the number of suspicious domains shared on social media during different phases of the pandemic. Our analysis reveals an increase in the number of suspicious domains during the lockdown compared to other lockdown phases. We observe that IT, Search Engines, and Businesses are the top three categories that contain suspicious domains. Our analysis reveals that adversaries' strategies to instigate malicious activities change with the country's pandemic situation.

翻译：在COVID-19封锁期间，社交媒体平台的使用量急剧攀升。这一封锁阶段催生了一系列新型网络犯罪，攻击者得以利用多种威胁手段侵害社交媒体用户。本文开展了一项大规模研究，旨在探究疫情及封锁期对社交媒体用户安全与隐私的影响。我们分析了过去533天数据爬取中收集到的1060万条与COVID相关的推文，并考察了用户在三个不同时期（即封锁前、封锁中及封锁后）的安全与隐私行为。研究表明，用户在撰写疫情相关推文时（例如分享附近新冠病毒检测点的位置），会无意中泄露更多个人可识别信息。若用户发布三条及以上涉及疫情的敏感推文，其隐私风险将达100%。我们进一步调查了疫情期间不同阶段社交媒体上分享的可疑域名数量。分析显示，相较于其他封锁阶段，封锁期间可疑域名的数量有所增长。我们观察到，信息技术、搜索引擎和商业是包含可疑域名的三大主要类别。分析还发现，攻击者实施恶意活动的策略会随各国疫情形势的变化而调整。