WASHINGTON : IBM is sounding the alarm over hackers targeting companies critical to the distribution of Covid-19 vaccines, a sign that digital spies are turning their attention to the complex logistical work involved in inoculating the world's population against the novel coronavirus.The information technology company said in a blog post published on Thursday that it had uncovered "a global phishing campaign" focused on organizations associated with the COVID-19 vaccine "cold chain" - the process needed to keep vaccine doses at extremely cold temperatures as they travel from manufacturers to people's arms.Also read: India’s quest to fix its payments puzzleThe US Cybersecurity and Infrastructure Security Agency reposted the report, warning.