EDIT: Since biblatex
v2.2, one may simply issue \renewcommand*{\revsdnamepunct}{}
in the document preamble.
\documentclass{article}
\usepackage[firstinits=true,terseinits=true]{biblatex}
\DeclareNameAlias{default}{last-first}
\renewcommand*{\revsdnamepunct}{}
\usepackage{filecontents}
\begin{filecontents}{\jobname.bib}
@misc{A01,
author = {Author, Aaa and Buthor, Bbb and Cuthor, Ccc},
year = {2001},
title = {Alpha},
}
\end{filecontents}
\addbibresource{\jobname.bib}
\nocite{*}
\begin{document}
\printbibliography
\end{document}

ORIGINAL ANSWER: Redefine the bibmacro name:last-first
.
\documentclass{article}
\usepackage[firstinits=true,terseinits=true]{biblatex}
\DeclareNameAlias{default}{last-first}
\renewbibmacro*{name:last-first}[4]{%
\ifuseprefix
{\usebibmacro{name:delim}{#3#1}%
\usebibmacro{name:hook}{#3#1}%
\ifblank{#3}{}{%
\ifcapital
{\mkbibnameprefix{\MakeCapital{#3}}\isdot}
{\mkbibnameprefix{#3}\isdot}%
\ifpunctmark{'}{}{\bibnamedelimc}}%
\mkbibnamelast{#1}\isdot
\ifblank{#4}{}{\bibnamedelimd\mkbibnameaffix{#4}\isdot}%
% \ifblank{#2}{}{\addcomma\bibnamedelimd\mkbibnamefirst{#2}\isdot}}% DELETED
\ifblank{#2}{}{\bibnamedelimd\mkbibnamefirst{#2}\isdot}}% NEW
{\usebibmacro{name:delim}{#1}%
\usebibmacro{name:hook}{#1}%
\mkbibnamelast{#1}\isdot
\ifblank{#4}{}{\bibnamedelimd\mkbibnameaffix{#4}\isdot}%
% \ifblank{#2#3}{}{\addcomma}% DELETED
\ifblank{#2}{}{\bibnamedelimd\mkbibnamefirst{#2}\isdot}%
\ifblank{#3}{}{\bibnamedelimd\mkbibnameprefix{#3}\isdot}}}
\usepackage{filecontents}
\begin{filecontents}{\jobname.bib}
@misc{A01,
author = {Author, Aaa and Buthor, Bbb and Cuthor, Ccc},
year = {2001},
title = {Alpha},
}
\end{filecontents}
\addbibresource{\jobname.bib}
\nocite{*}
\begin{document}
\printbibliography
\end{document}